ANALYSIS OF CHEMISTRY TEACHERS' COVALENT BOND CONCEPTUAL UNDERSTANDING THROUGH DIAGNOSTIC INTERVIEW TECHNIQUE

Conceptual understanding of the subject matter is crucial for teachers in conducting instruction. The covalent bond is one of the essential knowledge of chemistry. This knowledge underlies most of the chemistry body knowledge. The purpose of this study is to investigate the chemistry teachers' conceptual understanding of covalent bonds. This study applied a descriptive qualitative research design. The research subjects were eight chemistry teachers from different schools. Data collection was carried out using a diagnostic interview technique guided by the semistructured interview protocol. Data analysis was performed using phenomenography techniques. The results show that 25.00% of the interviewees well understood the covalent bond concepts, 22.75% do not understand, and 52.25% have misconceptions. Chemistry teachers have misconceptions about the concepts of intents of atom forming bonds, coordination bonds, types of atoms that form covalent bonds, polar and nonpolar covalent bonds, the level of covalent bonds polarity, Lewis structure writing, and covalent bond length.


INTRODUCTION
Conceptual understanding is one of the teachers' primary professional competence since it affects students' learning progress (Kleickmann et al., 2013). Their conceptual comprehension has been proven to impact the way teachers carry out their teaching (Baumert et al., 2010;Hill et al., 2005). Therefore, to create an effective learning process, teachers have to possess excellent conceptual understanding (Mavhunga & Rollnick, 2016). Besides, they also have to have a broader knowledge than the ones learned by the students (Bergqvist & Rundgren, 2017). The comprehension limitation and misconception cause students to experience learning difficulties and misconceptions (Kolomuç & Tekin, 2011).
Studies suggest that the covalent bond concept is presumed to be complicated by students and teachers (Bergqvist et al., 2016;Dhindsa & Treagust, 2014;Nahum et al., 2010). Ir is the fundamental concept in chemistry. The concepts within the covalent bond theory are the students' fundamental to understand ionic bonds (Dhindsa & Treagust, 2014). Additionally, the covalent bond is also related to the other chemical concepts, such as molecular structure, compound physical and chemical features, as well as chemical reaction (Özmen, 2004). However, the misconception on the covalent bond is frequently observed, such as the types of the atom with a covalent bond, the process of covalent bond formation, and types of covalent bonds (Ünal et al., 2010), the writing of Lewis structure (Ardiansah et al., 2014;Cooper et al., 2010), electronegativity (Eymur & Geban, 2017), octet rule (Luxford & Bretz, 2014;Ultay, 2015;Vrabec & Prokša, 2016), and the covalent bond length (Erman, 2016). The misconception of the covalent bond is found in senior high school students and college students (Burrows & Mooring, 2015;Luxford & Bretz, 2013). The misconception is even discovered in teachers of secondary schools (Ardiansah et al., 2014;Kolomuç & Tekin, 2011).
The research conducted by Ardiansah et al. (2014) on the high school chemistry teachers' understanding of chemical concept bonding reveals that only 21% of teachers know the concepts, while 57% have a misconception, and 22% of teachers do not know the concept. It indicates that teachers' understanding of chemical bonds is categorized as low. In other words, the teachers have not fulfilled the professional teacher standard competencies, which cover teacher wide and deep lesson mastery, with no misconception. Therefore, an analysis of teacher conceptual understanding is required as an initial step to improve the covalent bond learning quality.
Teachers' conceptual understanding of a concept can be measured using diagnostic interviews (Montfort et al., 2007). Among other misconception diagnostic methods, an interview has an essential role since it investigates deeper and aids in obtaining a more detailed description of the teacher's cognitive structure (Gurel et al., 2015). Even with guidelines, teachers' answers carry flexibility to researchers to ask more profound questions than the designated questions to attain a broader answer to the teacher's conceptual mastery (Adhabi & Anozie, 2017). Some studies have proven that the diagnostic interview reveals students' conceptual understanding (Linenberger & Bretz, 2012;Montfort et al., 2007;Ünal et al., 2010). Thus, this research aims to analyze the covalent bond conceptual understanding of chemistry teachers using diagnostic interviews.

METHOD
This research used a descriptive design with a qualitative approach. Descriptive research aims to describe teachers' understanding of the covalent bond concept. The qualitative approach was selected to attain a more profound meaning from the research findings, a complete overview of the research finding, and a detailed research process description. The subjects were eight chemistry teachers in Banten from different schools. The researchers acted as the primary instruments in the qualitative research while the interview guideline was used to guide the researchers to stay in the investigated topic. The selected interview type was a semi-structured interview, with interview guidelines had been validated by the chemistry lecturer in Universitas Negeri Malang. The obtained interview data were transcribed and went to a validity check through the member check technique. The data analysis was carried out referring to phenomenographic analysis framework (Ebenezer, 1996) consisting of transcribing the interview recording, coding the data to ease the searching process, reducing the data that is not related to the research focus, classifying data to categorize teachers' understanding based on the answer criteria of Abraham at al. (1992), presenting the data and creating the conclusion.

RESULTS AND DISCUSSION
The classified teachers' understanding of covalent bonds is presented in Table 2.    Figure 1 shows that the teachers with conceptual understanding offer the correct covalent bond example, while Figure 2 shows the teachers who understand the concept but fail to give the proper example. The teacher's mistakes in giving coordinate bond examples occur due to their inability to write the correct Lewis structure of H 2 SO 4 . The teachers' H2SO4 Lewis structure is not following the experimental fact and the formal charge of the atoms is not equal to zero. The interview results reveal that this misconception emerges since teachers follow the coordinate bond example provided in the textbook without reviewing the example. After the textbook was checked, the bond between atom O and S in the H 2 SO 4 molecule is the coordinate covalent. Similar results are also discovered in a study conducted by Erman (2016), that one of the misconception sources is the textbook. Therefore, the teachers have to be more thorough in selecting the textbook. They have also to ensure that the learning source has no misconception.
In addition, the data presented in Table 2 also shows that the average percentage of teachers with no conceptual understanding is 22.75%. This category is highly observed in the bond order concept (100%). The teachers said they forgot or had no idea about the bond order and the number of bond order among atoms on ethane, ethene, ethane molecule. All teachers do not understand that bond order is the number of covalent bonds that occur between two atoms. The amount of covalent bond among the C atoms on the ethane, ethene, and ethane are one, two, and three, respectively. Thus their bond order number are also one, two, and three, respectively. The bond order concept has to be comprehended by the teachers since this concept is closely related to the covalent bond length.
The molecule's formal charge concept and stability also present a high not understanding criteria percentage of 62.5%. The teachers in this category unable to explain and estimate the formal charge and explain the relationships among formal charge and stability of molecule or simple polyatomic ion. These teachers presume that this concept is not essential to be taught to the students, as indicated in the interview answer on the formal charge concept below: Researcher : "in the Lewis structure, those atoms have a formal charge. Do you remember what is the formal charge?" Teacher : "I forgot, since it is not taught in school, so I forget the definition of formal charge," Researcher : "Why is it not taught?" Teacher : "The book does not mention it, so it is not taught." That part of the interview answer indicates that the teacher considers the formal charge concept as not a significant concept in the learning process and is not discussed in the textbook. Thus, the teachers do not remember and look for that concept. Teachers should have understood the concept of formal charge since it is used to determine the molecules or polyatomic ion stability in the covalent bond learning. Therefore, as the information source, teachers should have a broader and deeper knowledge since one of the causes of misconception is the teacher's limited information (Erman, 2016).
Table 2 also shows that the misconception category attains the highest percentage of 52.25%. The observed misconceptions are presented in Table 3. The polar covalent bond is the covalent bond with PEB in its centers, such as H2O and NH3. The nonpolar covalent bond is the covalent bond with no PEB in its center, such as CH4and F2.

50%
The atoms on the polar covalent bond have great electronegativity difference, such as HCl. The atoms on a nonpolar covalent bond have a small or zero electronegativity difference, such as H2. 1 The polar covalent bond is marked by different atoms, such as HCl. The nonpolar covalent bond is marked by the same atom, such as H2. 1 The order of polarity of covalent bonds The polarity of bond HF > HCl > HBr since the atom size F < Cl <Br. 1 50% The polarity of bond HF > HCl > HBr since F can form a hydrogen bond and ordered based on the atom size, and a smaller atom size indicates more polarity.
1 HF, HCl, and HBr has the same polarity bond 2 Lewis Structure The Lewis Structure of NO2 is: 3 100% The Lewis Structure of NO2 is:

5
Atoms that follow the octet rule The always octet center atom is the atom type IV and V 1 100% The always octet center atom is the atom type halogen, and atom C 2 The always octet center atom is the nonmetal atom 1 The always octet center atom is the atom C, N, O, F, Cl, Br, I 3 The always octet center atom is the atom type IVA and VIA 1 Atoms that can be less than or maximal of octet The center atom with valence shell that can be less than octet is H and atom type II 1 100% The center atom with valence shell that can be less than octet is atom Be 4 The center atom with valence shell that can be less than octet is Be and B 2 The center atom with a valence shell that can be less than octet is atom S 1 Atoms that can be more than octet The center atom with valence shell that can be more than octet is atom type VI 1 100% The center atom with valence shell that can be more than octet is period three atom 1 The center atom with valence shell that can be more than octet is atom P and S 3 The center atom with a valence shell that can be more than an octet is atom S 3 Bond length on ethane, ethene, ethane The bond length among atom C on ethane = ethane = ethane 2 25% Bond length on HF, HCl, and HBr The bond length HF > HCl > HBr since the electronegativity F > Cl > Br 2 37,5% The bond length HF = HCl = HBr 1 Table 3 shows that the highest misconception percentage is identified in the Purposes of bonded atoms, Lewis structure writing, and octet rules that reach 100%. The recognized teachers' understanding of the Lewis structure writing is that they can correctly write the Lewis structure of the simple molecule, such as HF, HCl, H 2 , and HC 4 molecules. However, they find difficulties in writing the Lewis structure of the NO 2 molecule. The interview results reveal that the teachers' stages in writing Lewis structure include (1) determining the electron configuration of each atom; (2) deciding the center atom; (3) illustrating the Lewis symbol of each atom; (4) pairing each electron from each atom, to form octet or duplet. Those steps generate difficulties for teachers to write the non-octet Lewis structure. All teachers cannot correctly write the Lewis structure of the NO 2 molecule, as illustrated in Figures 3 and 4.  Figure 3 is the Lewis structure drawn by the teacher who understood the formal charge concept. The teacher draws the Lewis structure of the NO2 molecule by making the formal charge of allatom zero. The mistakes in Figure 3 happen since the valence shell of the N atom has nine electrons. The teachers do not understand that the maximum 2 periods atoms in the valence shell in the octet rule are only eight. N atom is one of the 2 periods atoms, so that it can not have more than eight electrons. Figure 4 is the Lewis structure made by teachers with no understanding of the formal electron charge that emphasizes the fulfillment of the octet rule on both O atoms without considering the formal charge. These teachers' mistakes are that the formal charge of both O atoms is not equal to zero, while the stable Lewis structure should have minimal or close to zero formal charges.
The mistake in the Lewis structure writing caused by the octet rules fulfillment focus has also been identified in a study carried out by Ardiansah et al. (2014); Cooper et al. (2010); Nurbaity & Mustikasari (2012). Consequently, other than the octet rule, the formal charge concept should also be used to write the Lewis structure. The comfortable and correct Lewis structure writing is presented by the steps arranged by Effendy (2017). The stages consist of (1) determining the center atom, (2) estimating the BK of the center atom, PEI, and PEB, (3) write the Lewis structure framework, (4) concretizing all substituents, (5) calculating the formal charge of each atom, and (6) transforming the formal charge of the atom equals to zero, and if possible, by changing the PEB into the π bond.

CONCLUSIONS
The teachers' conceptual understanding of covalent bond has not been satisfying (25% understand the concept, 22.75% do not understand the idea, and 52.25% experience misconception). The misconception is observed on the purpose of bond atoms, covalent and coordinate bond, types of atoms that form a covalent bond, polar and nonpolar covalent bond, the polarity order of covalent bond, and the length of a covalent bond.
The findings from this research confirm the teachers' low covalent bond understanding. That finding should be followed up by (1) identification of ways to accelerate teachers' conceptual understanding of covalent bond, (2) efforts to improve the teaching quality, including the improvement on teachers' conceptual understanding, and (3) analysis of chemistry teachers' conceptual understanding on other chemistry constructs.