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Chapter 8: Problem 9

(a) True or false: An element's number of valence electrons is the same as its atomic number. (b) How many valence electrons does a nitrogen atom possess? (c) An atom has the electron configuration $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{2} .$ How many valence electrons does the atom have?

Short Answer

Expert verified
(a) False, an element's number of valence electrons is not always the same as its atomic number. (b) A nitrogen atom has 5 valence electrons. (c) The atom with the electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^2\) has 4 valence electrons.

Step by step solution

01

(a) Analyze the statement

Valence electrons are the electrons in an atom's outermost shell, and they determine an element's chemical properties. The atomic number, on the other hand, is the number of protons in an atom's nucleus and is equal to the number of electrons in a neutral atom. So, we need to evaluate if the number of valence electrons is always equal to the atomic number.
02

(a) Determine the truth of the statement

Considering elements like hydrogen (atomic number = 1, valence electrons = 1) and helium (atomic number = 2, valence electrons = 2), the statement might seem true. However, let's take a look at lithium (atomic number = 3). Its electron configuration is \(1s^2 2s^1\), which means it has 1 valence electron in its outermost shell (that is the second shell), which is not equal to its atomic number. Thus, the statement is false.
03

(b) Identify Nitrogen's electron configuration

Nitrogen has an atomic number of 7. Its electron configuration follows the aufbau principle, filling up the levels in this order: \(1s^2 2s^2 2p^3\).
04

(b) Find the number of valence electrons in Nitrogen

Nitrogen's outermost shell is the 2nd shell, which has the electron configuration \(2s^2 2p^3\). Valence electrons are the total electrons in this shell: \(2+3 = 5\). So, a nitrogen atom has 5 valence electrons.
05

(c) Identify the given atom's valence electrons

We are given an atom with electron configuration \(1s^2 2s^2 2p^6 3s^2 3p^2\).
06

(c) Determine the number of valence electrons

The outermost shell in this electron configuration is the 3rd shell, with the electron configuration \(3s^2 3p^2\). Valence electrons are the total electrons in this shell: \(2+2 = 4\). Thus, this atom has 4 valence electrons.

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Most popular questions from this chapter

A classmate of yours is convinced that he knows everything about electronegativity. (a) In the case of atoms X and Y having different electronegativities, he says, the diatomic molecule \(X-Y\) must be polar. Is your classmate correct? (b) Your classmate says that the farther the two atoms are apart in a bond, the larger the dipole moment will be. Is your classmate correct?

A common form of elemental phosphorus is the white phosphorus, where four \(\mathrm{P}\) atoms are arranged in a tetrahedron. All four phosphorus atoms are equivalent. White phosphorus reacts spontaneously with the oxygen in air to form \(\mathrm{P}_{4} \mathrm{O}_{6} .\) (a) How many valance electron pairs are in the \(\mathrm{P}_{4} \mathrm{O}_{6}\) molecule? (b) When $\mathrm{P}_{4} \mathrm{O}_{6}\( is dissolved in water, it produces a \)\mathrm{H}_{3} \mathrm{PO}_{3}\(, molecule. \)\mathrm{H}_{3} \mathrm{PO}_{3}$ has two forms, \(\mathrm{P}\) forms 3 covalent bonds in the first form and \(\mathrm{P}\) forms 5 covalent bonds in the second form. Draw two possible Lewis structures of \(\mathrm{H}_{3} \mathrm{PO}_{3}\). (c) Which structure obeys the octet rule?

A new compound is made that has a \(\mathrm{C}-\mathrm{N}\) bond length of $118 \mathrm{pm}$. Is this bond likely to be a single, double, or triple C-N bond?

1,2-dihydroxybenzene is obtained when two of the adjacent hydrogen atoms in benzene are replaced with an OH group. A skeleton of the molecule is shown here. (a) Complete a Lewis structure for the molecule using bonds and electron pairs as needed. (b) Are there any resonance structures for the molecule? If so, sketch them. (c) Are the resonance structures in (a) and (b) equivalent to one another as they are in benzene?

List the individual steps used in constructing a Born-Haber cycle for the formation of BaI \(_{2}\) from the elements. Which of the steps would you expect to be exothermic?
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