Chemistry 1.0: Lewis Structures and Octet Rule

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Questions and Answers

What happens during the formation of an ionic bond?

Electrons are shared equally between atoms.

Electrons are lost by both atoms in a bond.

Electrons are transferred from the atom with lower electronegativity to the atom with higher electronegativity. (correct)

Electrons are transferred from the atom with higher electronegativity to the one with lower electronegativity.

In a Lewis structure of ions, what does the superscript indicate?

The charge of the ion. (correct)

The number of valence electrons.

The atomic number of the element.

The total number of electrons in the atom.

Which of the following correctly represents the electron sharing in covalent bonds?

Only valence electrons are considered in bonding.

Electrons are completely transferred.

Electrons are shared in pairs. (correct)

All electrons from both atoms are involved in bonding.

Which characteristic is true of metals in the context of ionic bonding?

They lose electrons during the formation of ionic bonds. Signup and view all the answers

How many electrons does Sodium (Na) lose to form a Sodium ion?

1 electron Signup and view all the answers

When drawing the Lewis structure for a molecule like KCl, what does the bracketed format represent?

The ionic nature of the bond between K and Cl. Signup and view all the answers

Which statement correctly describes the lone pairs in covalent bonding?

They do not participate in bonding. Signup and view all the answers

For the compound CaCl2, what is the charge on the calcium ion?

+2 Signup and view all the answers

Which of the following correctly describes a cation?

A positively charged ion formed by losing electrons. Signup and view all the answers

What is the significance of reaching an octet configuration?

It imparts high stability, causing noble gases to be mostly unreactive. Signup and view all the answers

Which of the following is true about the representation of ions using Lewis structures?

The number of dots in a Lewis structure reflects the electrons gained or lost. Signup and view all the answers

How did Gilbert Lewis contribute to understanding valence electrons?

He introduced electron-dot structures to represent valence electrons. Signup and view all the answers

Which of the following statements about anions is correct?

Anions are negatively charged due to the gain of electrons. Signup and view all the answers

What does an octet mean in the context of chemical bonding?

A stable electronic configuration involving eight electrons in the valence shell. Signup and view all the answers

What is the main reason noble gases are chemically inert?

They have a complete octet configuration with no tendency to gain or lose electrons. Signup and view all the answers

In Lewis structures, how are valence electrons typically represented?

As dots surrounding the element's symbol. Signup and view all the answers

Study Notes

Chemistry 1.0 Competencies

Draw Lewis structures of ions
Apply the octet rule in forming molecular covalent compounds

Ion Formation

Atoms gain or lose electrons to form ions
Cations are positively charged ions formed by losing electrons, increasing proton count
Anions are negatively charged ions formed by gaining electrons, increasing electron count
Example: Magnesium ion (Mg²⁺), Oxide ion (O²⁻)

Octet Rule

"Octet" from Greek word "okto", meaning "eight"
Octet configuration is the most stable electron arrangement for atoms
Noble gases are stable because they have a full octet of valence electrons
Atoms tend to gain, lose, or share electrons to achieve a stable octet configuration, affecting chemical reactions
Atoms with fewer than eight valence electrons tend to bond with other atoms to achieve an octet

Octet Rule (Periodic Table)

Atoms in the periodic table seek a stable noble gas configuration
Achieving this configuration involves reacting with other elements to form stable compounds

Gilbert N. Lewis (1875-1946)

In 1916, developed a system for representing valence electrons of atoms
Called Lewis's electron-dot structures or Lewis structures

Lewis Structure: Hydrogen

Element symbol (H) surrounded by dots
Dots represent valence electrons (1 valence electron)
Two dots are placed on each side of the symbol

Lewis Structure: Oxygen

Arrangement of dots around oxygen symbol may vary, but represents valence electrons(6 valence electrons)

Lewis Structures and Ions

Ions are represented by Lewis structures by adding or subtracting dots to reflect lost or gained electrons in the neutral atom
Example: Sodium (Na) loses a single electron to form a structure with a +1 charge

Example: Sodium Ion (Na⁺)

Element: Sodium (Na)
Electron configuration: 1s², 2s², 2p⁶, 3s¹
Valence electrons: 1
Neutral atom loses one electron: Na → Na⁺

Activity 3

Students must find a stained glass example
Students must create an A4 size paper with the stained glass sample
Chemistry concepts must be included detailing the sample

Lewis Structure of Ionic Compounds

In ionic compounds like NaCl, electrons are transferred from one atom to another (NaCl) forming an ionic bond
Atoms with different electronegativity values are involved in forming an ionic bond
The atom with lower electronegativity transfers its electron to the atom with higher electronegativity
Metals have lower electronegativity values than nonmetals.

Example: NaCl

Sodium (Na) loses one electron to form Na⁺
Chlorine (Cl) gains one electron to form Cl⁻
The resulting ions are held together by electrostatic forces forming NaCl

Example: Li₂S

Lithium (Li) loses one electron to form Li⁺, while Sulfur (S) gains two electrons to form S²⁻
These ions are held together electrically to form Li₂S

Lewis Structure of Ions

In a Lewis structure for ions, the element symbol is in brackets with a superscript representing the charge
Cations lose valence electrons
Anions gain valence electrons (obtained by cations)

Example: KCl

Potassium (K) loses one electron (creating a K⁺ ion)
Chlorine (Cl) gains one electron (creating a Cl⁻ ion)

Example: CaCl₂

Calcium (Ca) loses two electrons (creating a Ca²⁺ ion)
Chlorine (Cl) gains one electron to form Cl⁻

Lewis Structure of Covalent Compounds

Covalent bonding involves sharing electrons between two or more atoms
This satisfies the octet rule—ensuring chemical stability
Involves two or more nonmetals
Shared electrons are called bonding electrons; unshared electrons are lone pairs

Example: HCl

Hydrogen (H) and Chlorine (Cl) Atoms share electrons to establish a covalent bond

Example: H₂O

Oxygen (O) and Hydrogen (H) share electrons to form covalent bonds in water

Practice Problem

Table with spaces for drawing Lewis structures, identifying neutral atoms, and counting lost or gained electrons for elements C, Br, Al, and Rb.

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Description

Test your understanding of Lewis structures and the octet rule in molecular chemistry. This quiz covers ion formation, cations, anions, and the significance of achieving a stable electron configuration. Sharpen your skills in recognizing how electrons play a crucial role in chemical bonding.