Path to Mastering LT 4.2 - physical Properties and the PT

What is the number of valence electrons in an oxygen atom?

• 4

• 6

• 8

• 2

Answer explanation

We can use the group number of oxygen to help us figure out the number of valence electrons it has. Since oxygen is in group 16, you can subtract 10 from the group number to get the number of valence electrons. Also, oxygen has an atomic number of 8, meaning it has 8 electrons. The electron configuration shows that 2 electrons are in the first shell and 6 in the second shell, making the number of valence electrons 6.

How many energy levels does a neutral chlorine atom have?

• 1

• 2

• 3

• 4

Answer explanation

The number of energy levels that an atom has is indicated by the period (row) number. Since Chlorine is in period 3 of the periodic table, it has 3 energy levels. Also, a neutral chlorine atom has 17 electrons, which are arranged in three energy levels: 2 in the first, 8 in the second, and 7 in the third. Therefore, the correct answer is 3 energy levels.

Explain why elements in the same group of the periodic table have similar chemical properties.

• They have the same number of protons.

• They have the same number of valence electrons.

• They have the same atomic mass.

• They have the same number of neutrons.

Answer explanation

Elements in the same group have similar chemical properties because they possess the same number of valence electrons. This similarity in valence electrons leads to comparable reactivity and bonding behavior.

Compare the reactivity of alkali metals with that of alkaline earth metals.

• Alkali metals are less reactive than alkaline earth metals.

• Alkali metals are more reactive than alkaline earth metals.

• Both have the same reactivity.

• Reactivity depends on the specific element.

Answer explanation

Alkali metals (Group 1) are more reactive than alkaline earth metals (Group 2) due to their single valence electron, which they lose easily. In contrast, alkaline earth metals have two valence electrons, making them less reactive.

Analyze why nonmetals tend to gain electrons during chemical reactions.

• Nonmetals have high ionization energies.

• Nonmetals have low electronegativity.

• Nonmetals have high electronegativity.

• Nonmetals have low ionization energies.

Answer explanation

Nonmetals have high electronegativity, meaning they have a strong tendency to attract electrons during chemical reactions. This property drives them to gain electrons, forming negative ions.

Evaluate the statement: "The reactivity of halogens decreases as you move down the group." Provide a reason for your answer.

• True, because atomic size increases.

• False, because atomic size decreases.

• True, because electronegativity increases.

• False, because electronegativity decreases.

Answer explanation

True, because atomic size increases. As you move down the group of halogens, the atomic size increases, which leads to a decrease in reactivity due to the outer electrons being further from the nucleus and less tightly held.