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Chemistry - Chemical Bonding

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    Study Guide Chemistry – Chemical Bonding 1. Covalent Bonds 1. 1 What Makes Atoms Stable? Atoms are most stable when their outermost electron shell is full. This means: • The s - subshell is filled , and • The p - subshell is also filled . Only five elements naturally have completely filled valence shells. These are the inert (noble) gases , found in the far - right column of the periodic table. Because their electron shells are already full, they do not usually react with other elements. All other elements are not stable on their own . To become stable, their atoms must either gain, lose, or share electrons . 1. 2 How Atoms Become Stable Most atoms reach stability by sharing electrons with other atoms . This type of sharing forms a covalent bond . Scientists often use Lewis diagrams to show this process. In these diagrams: • Each valence electron is shown as a dot • Only the outer - shell electrons are drawn

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    Study Guide Example: Fluorine Atoms Fluorine is element number 9. Its electron configuration is: 1s² 2s² 2p⁵ This means: • It has 7 valence electrons • It needs 1 more electron to become stable Each fluorine atom has one unpaired electron. When two fluorine atoms come close , they can share one electron each . Together:

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    Study Guide • Each atom now has 8 electrons • The shared pair forms a covalent bond • The molecule formed is F ₂ There are 14 electrons total , with each atom contributing 7. 1. 3 Counting Valence Electrons You can find the number of valence electrons by counting columns in the periodic table (for main - group elements). For example: • Phosphorus has 5 valence electrons • Chlorine has 7 valence electrons Figure 3. Counting valence electrons. 1. 4 Forming the PCl ₃ Molecule Phosphorus needs 3 more electrons to complete its outer shell. Each chlorine needs 1 electron . So: • One phosphorus atom bonds with three chlorine atoms • Six electrons are shared in total

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    Study Guide Important points: • All atoms now have 8 valence electrons • 6 electrons are shared • 20 electrons remain unshared • Phosphorus contributes 3 electrons • Each chlorine contributes 1 electron 1. 5 Structural Formulas Chemists often simplify Lewis diagrams by using lines instead of dots . • One line = one shared pair of electrons • This drawing is called a structural formula • Nonbonding electrons are sometimes omitted for clarity 1. 6 Hydrogen Chloride (HCl) Hydrogen is different from most elements: • It only needs 2 electrons to fill its shell In hydrogen chloride: • Hydrogen shares 1 electron • Chlorine shares 1 electron

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    Study Guide • Both atoms become stable In the molecule: • Hydrogen has 2 electrons • Chlorine has 8 electrons 1. 7 Double Bonds Sometimes atoms share more than one pair of electrons . In ethylene (C ₂ H ₄ ) : • Two carbon atoms share four electrons • This forms two shared pairs Because: • One shared pair = one covalent bond • Two shared pairs = a double bond This is shown using two lines between atoms. 1. 8 Triple Bonds Some molecules share three pairs of electrons . In the nitrogen molecule (N ₂ ) :

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    Study Guide • Each nitrogen atom has 5 valence electrons • Six electrons are shared • Four electrons are nonbonding Figure 8.A double bond between two carbon atoms. Figure 9.A triple bond between two nitrogen atoms. The three shared pairs form a triple bond , shown as three lines . 2. Quiz: Covalent Bonds 1. Question The electrons involved in bonding are Answer Choices • found closest to the nucleus • found in the nucleus • found in the highest occupied energy level(s) Correct Answer found in the highest occupied energy level(s) Why This is Correct

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    Study Guide Electrons that participate in chemical bonding are called valence electrons . These electrons are located in the outermost (highest occupied) energy level of an atom, where they can interact with electrons from other atoms to form bonds. For Example In a sodium atom, the single electron in the outermost shell is involved in bonding, not the electrons close to the nucleus. 2. Question Atoms in a molecule are held together by Answer Choices • the strong nuclear force • chemical bonds • gravity Correct Answer chemical bonds Why This is Correct Atoms in a molecule are connected by chemical bonds , which form when atoms share or transfer electrons. These bonds hold the atoms together in a stable arrangement. For Example In a water molecule (H ₂ O), chemical bonds hold the hydrogen and oxygen atoms together, allowing the molecule to exist as a single substance. 3. Question When atoms share valence electrons, a(n) __________ is formed.

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    Study Guide Answer Choices • covalent bond • ionic bond • metallic bond Correct Answer covalent bond Why This is Correct A covalent bond forms when atoms share valence electrons so that each atom can achieve a more stable electron configuration. Ionic bonds involve electron transfer, and metallic bonds involve a “sea of electrons,” not sharing between specific atoms. For Example In a water molecule (H ₂ O), hydrogen and oxygen atoms share electrons, forming covalent bonds. 4. Question Typically, when two atoms form a chemical bond, the expected result is that the electrons Answer Choices • will be in the excited state • will be completely removed from both atoms • will complete a noble gas configuration for both atoms Correct Answer will complete a noble gas configuration for both atoms Why This is Correct

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    Study Guide Atoms form chemical bonds in order to become more stable. By gaining, losing, or sharing electrons, atoms usually achieve a noble gas configuration , meaning a full outer energy level. This stable arrangement lowers the atom’s energy. For Example When sodium bonds with chlorine, sodium loses one electron and chlorine gains one, allowing both atoms to achieve stable noble gas configurations. 5. Question Generally speaking, when two nonmetals form a chemical bond, the bond is a(n) Answer Choices • covalent bond • ionic bond • metallic bond Correct Answer covalent bond Why This is Correct When two nonmetals bond, they tend to share electrons rather than transfer them. This sharing of electrons forms a covalent bond . Ionic bonds usually occur between metals and nonmetals, and metallic bonds occur between metal atoms only. For Example In a water molecule (H ₂ O), hydrogen and oxygen are both nonmetals and share electrons, forming covalent bonds. 6. Question What type of diagram uses a single dot to represent an electron?

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    Study Guide Answer Choices • Dalton diagram • Thomson diagram • Lewis diagram Correct Answer Lewis diagram Why This is Correct A Lewis diagram represents valence electrons as dots around the chemical symbol of an element. Each dot stands for one electron involved in bonding. For Example The Lewis diagram of oxygen shows six dots around the symbol O , representing its six valence electrons. 7. Question Typically, when forming a chemical bond, the goal is to achieve __________ electrons in the outermost energy shell? Answer Choices • 2 • 6 • 8 Correct Answer 8 Why This is Correct

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