25. why is a hydrogen molecule (h₂) more stable than two separate hydrogen atoms?
26. what is a double bond, and how is it different from a single covalent bond?
27. how many double bonds are present in a carbon dioxide (co₂) molecule?
28. what happens to electrons during ionic bonding?
29. why does sodium form a positive ion while chlorine forms a negative ion?
30. how does the attraction between ions differ from the sharing of electrons in covalent bonds?
31. why are ionic compounds more stable after ions form?

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Accepted Answer

### Question 25
# Brief Explanations:
A hydrogen atom has 1 valence electron and needs 1 more to fill its outer shell (duet rule). In $\ce{H_2}$, the two H atoms share their electrons, forming a covalent bond. This sharing gives each atom a stable electron configuration (like helium, 2 electrons in the outer shell), lowering the overall energy of the system compared to two separate atoms with unpaired electrons seeking stability.
# Answer:
A hydrogen molecule ($\ce{H_2}$) is more stable because the two H atoms share electrons to form a covalent bond, giving each atom a stable electron configuration (duet of electrons), which lowers the system's energy compared to two separate H atoms with unpaired electrons.

### Question 26
# Brief Explanations:
A double bond is a covalent bond where two atoms share two pairs of electrons (4 total electrons). A single covalent bond involves sharing one pair (2 electrons). Differences: 1. Electron pairs: double has 2, single has 1. 2. Bond length: double bonds are shorter. 3. Bond energy: double bonds have higher energy (harder to break) than single bonds. 4. Reactivity: double bonds are more reactive (due to extra electron density) than single bonds in many cases.
# Answer:
A double bond is a covalent bond with two shared electron pairs (4 electrons) between atoms. It differs from a single covalent bond (1 electron pair, 2 electrons) by having more shared electrons, shorter length, higher energy, and often greater reactivity.

### Question 27
# Explanation:
## Step1: Determine the Lewis structure of $\ce{CO_2}$
Carbon (C) has 4 valence electrons, and each oxygen (O) has 6. The total valence electrons are $4 + 2	imes6 = 16$. Carbon is the central atom. We arrange the atoms as O - C - O.
## Step2: Form bonds and lone pairs
We start by forming single bonds: O - C - O (2 bonds, 4 electrons used). Remaining electrons: $16 - 4 = 12$. We place 6 electrons (3 pairs) on each O, but this would give O atoms 7 electrons (not stable, needs 8). So we convert lone pairs to double bonds. Each O needs 2 more electrons, so we form two double bonds (O = C = O). Now, each O has 8 electrons (2 from double bond, 6 from lone pairs), and C has 8 (4 from two double bonds).
## Step3: Count double bonds
In the Lewis structure O = C = O, there are two double bonds.
# Answer:
There are 2 double bonds in a $\ce{CO_2}$ molecule.

### Question 28
# Brief Explanations:
In ionic bonding, electrons are transferred from one atom to another. Typically, a metal (electron donor, low electronegativity) transfers one or more valence electrons to a non - metal (electron acceptor, high electronegativity). For example, in $\ce{NaCl}$ formation, sodium (Na) has 1 valence electron. It transfers this electron to chlorine (Cl), which has 7 valence electrons. Na becomes $\ce{Na^+}$ (loses electron), and Cl becomes $\ce{Cl^-}$ (gains electron). The transfer results in the formation of ions with stable electron configurations (like noble gases), and the oppositely charged ions are then attracted to each other.
# Answer:
During ionic bonding, electrons are transferred from a metal (or less electronegative atom) to a non - metal (or more electronegative atom), forming positively charged cations (electron - donors) and negatively charged anions (electron - acceptors).

### Question 29
# Brief Explanations:
Sodium (Na) has an electron configuration of $1s^22s^22p^63s^1$. It has 1 valence electron in the 3s orbital. To achieve a stable electron configuration (like neon, $1s^22s^22p^6$), it is energetically favorable for sodium to lose this 1 valence electron. When it loses the electron, it forms a $\ce{Na^+}$ ion (positive ion) with a stable octet (or duet - like for the inner shell, but the outer shell now has 8 electrons like neon). Chlorine (Cl) has an electron configuration of $1s^22s^22p^63s^23p^5$. It has 7 valence electrons. To achieve a stable electron configuration (like argon, $1s^22s^22p^63s^23p^6$), it is energetically favorable for chlorine to gain 1 electron. When it gains an electron, it forms a $\ce{Cl^-}$ ion (negative ion) with a stable octet.
# Answer:
Sodium forms a positive ion because it loses its 1 valence electron to achieve a stable noble - gas - like electron configuration (neon - like). Chlorine forms a negative ion because it gains 1 electron to achieve a stable noble - gas - like electron configuration (argon - like).

### Question 30
# Brief Explanations:
1. **Ionic bond (attraction between ions)**: It is an electrostatic attraction between oppositely charged ions (cations and anions). The force is due to the opposite charges, and it is a non - directional force (acts in all directions between ions in a lattice). The strength of the ionic attraction depends on the magnitude of the ion charges and the distance between them (Coulomb's law: $F=\frac{kq_1q_2}{r^2}$, where $k$ is a constant, $q_1,q_2$ are ion charges, and $r$ is the distance between ions).
2. **Covalent bond (sharing of electrons)**: It involves the sharing of one or more pairs of electrons between atoms. The shared electrons are attracted to the nuclei of both atoms, creating a bond. Covalent bonds are directional (the shared electron pair is concentrated between the two bonded atoms), and the strength depends on the number of shared electron pairs (single, double, triple bonds have increasing strength) and the atoms involved.
In summary, ionic attraction is electrostatic between charged ions, while covalent bonding is due to shared electron pairs attracting atomic nuclei.
# Answer:
Ionic attraction is electrostatic between oppositely charged ions (non - directional, depends on ion charges and distance). Covalent bonding is electron - pair sharing between atoms (directional, depends on shared pairs and atoms), differing in nature (attraction vs. sharing), directionality, and strength determinants.

### Question 31
# Brief Explanations:
When ions form, ionic compounds are more stable because: 1. **Electron configuration**: The ions have stable electron configurations (like noble gases). For example, in $\ce{NaCl}$, $\ce{Na^+}$ has a neon - like configuration and $\ce{Cl^-}$ has an argon - like configuration. 2. **Electrostatic attraction**: Oppositely charged ions (cations and anions) are strongly attracted to each other by Coulombic forces. This attraction lowers the overall energy of the system. 3. **Lattice structure**: Ions arrange themselves in a regular lattice structure, maximizing the attractive forces between oppositely charged ions and minimizing the repulsive forces between like - charged ions. The lattice energy (energy released when ions form a lattice) is negative, indicating a stable state.
# Answer:
Ionic compounds are more stable after ions form because ions have stable noble - gas - like electron configurations, and the strong electrostatic attraction between oppositely charged ions (in a lattice) lowers the system's energy.

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QUESTION IMAGE

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Explanation:

Question 25

Step1: Determine the Lewis structure of $\ce{CO_2}$

Step2: Form bonds and lone pairs

Step3: Count double bonds

Answer:

Question 26