Question

What is the total number of valence electrons in each of the following molecules? a. \(\mathrm{HNO}_{3}\) b. \(\mathrm{H}_{2} \mathrm{SO}_{4}\) c. \(\mathrm{H}_{3} \mathrm{PO}_{4}\) d. \(\mathrm{HClO}_{4}\)

Short answer

The total number of valence electrons for each molecule is: a. HNO3: 24 valence electrons b. H2SO4: 32 valence electrons c. H3PO4: 32 valence electrons d. HClO4: 32 valence electrons

Step-by-step solution

a. HNO3

In the HNO3 molecule, we have the elements hydrogen (H), nitrogen (N), and oxygen (O): - Hydrogen (H) has 1 valence electron. - Nitrogen (N) has 5 valence electrons. - Oxygen (O) has 6 valence electrons. In the HNO3 molecule, we have 1 hydrogen atom, 1 nitrogen atom, and 3 oxygen atoms: - Total valence electrons = (1 x 1) + (1 x 5) + (3 x 6) = 1 + 5 + 18 = 24 valence electrons.

b. H2SO4

In the H2SO4 molecule, we have the elements hydrogen (H), sulfur (S), and oxygen (O): - Hydrogen (H) has 1 valence electron. - Sulfur (S) has 6 valence electrons. - Oxygen (O) has 6 valence electrons. In the H2SO4 molecule, we have 2 hydrogen atoms, 1 sulfur atom, and 4 oxygen atoms: - Total valence electrons = (2 x 1) + (1 x 6) + (4 x 6) = 2 + 6 + 24 = 32 valence electrons.

c. H3PO4

In the H3PO4 molecule, we have the elements hydrogen (H), phosphorus (P), and oxygen (O): - Hydrogen (H) has 1 valence electron. - Phosphorus (P) has 5 valence electrons. - Oxygen (O) has 6 valence electrons. In the H3PO4 molecule, we have 3 hydrogen atoms, 1 phosphorus atom, and 4 oxygen atoms: - Total valence electrons = (3 x 1) + (1 x 5) + (4 x 6) = 3 + 5 + 24 = 32 valence electrons.

d. HClO4

In the HClO4 molecule, we have the elements hydrogen (H), chlorine (Cl), and oxygen (O): - Hydrogen (H) has 1 valence electron. - Chlorine (Cl) has 7 valence electrons. - Oxygen (O) has 6 valence electrons. In the HClO4 molecule, we have 1 hydrogen atom, 1 chlorine atom, and 4 oxygen atoms: - Total valence electrons = (1 x 1) + (1 x 7) + (4 x 6) = 1 + 7 + 24 = 32 valence electrons.

Key concepts

Chemical Bonding

Chemical bonding is the process that holds atoms together to form molecules or compounds. At the core of chemical bonding is the interaction of valence electrons. Valence electrons are the electrons in the outermost shell of an atom and are crucial in bond formation.

There are several types of chemical bonds, and understanding them is vital:

• Covalent Bonds: Atoms share valence electrons to achieve stability. This type of bonding is common between non-metals.
• Ionic Bonds: Involves the transfer of electrons from one atom to another, typically between metals and non-metals. This transfer creates positively and negatively charged ions.
• Metallic Bonds: Found in metals, where electrons are freely shared among a lattice of atoms.

Bonding affects the chemical and physical properties of a molecule including its shape, reactivity, and state of matter. Understanding the valence electrons involved helps predict how atoms will bond.

Electron Configuration

Electron configuration refers to the distribution of electrons in the atomic orbitals of an atom. It's like a map of where electrons are likely to be found around an atom's nucleus.

Each element has a unique electron configuration that determines its chemical properties. The order in which electrons are arranged is based on the principles of quantum mechanics and follows the Aufbau principle, Hund’s rule, and the Pauli exclusion principle. The electron configuration is usually noted by numbers and letters, such as 1s² 2s² 2p⁶. Important aspects include:

• Energy Levels: Represented by numbers (1, 2, 3...), they indicate the shell of the electron.
• Sublevels: Indicated by letters (s, p, d, f), these represent the shape of the electron's path.
• Valence Electrons: Found in the highest energy level, they participate in bond formation.

Understanding electron configuration helps explain how atoms combine and interact during chemical reactions.

Molecule Structure

The structure of a molecule is determined by the way its atoms are arranged in space. The shape of a molecule affects its function and reactivity, so understanding it is crucial in chemistry.

The shape is defined by the molecule's bonds and the arrangement of atoms. Common structures include:

• Linear: Atoms are arranged in a straight line.
• Tetrahedral: A central atom surrounded by four atoms at 109.5° angles.
• Trigonal Planar: Three atoms connected to a central atom lying in a plane.
• Bent: Two atoms bonded to a central atom with a bent shape due to lone pairs.

Valence Shell Electron Pair Repulsion (VSEPR) theory is often used to predict molecular structure based on electron pairs' repulsion. Understanding molecule structures helps in visualizing chemical reactions and properties.