rows of the periodic table are called

HESI A2

Chemistry HESI A2 Quizlet

1. What are the horizontal rows of the periodic table called?

A. Periods
B. Families
C. Groups
D. Columns

Correct answer: A

Rationale: The correct answer is A: Periods. Rows in the periodic table are called periods. They are arranged horizontally from left to right and represent the energy levels of the elements. Each period starts a new energy level or shell, indicating the number of electron shells an element has. Choices B, C, and D are incorrect. Families and groups refer to vertical columns in the periodic table that share similar chemical properties, while columns are vertical arrangements of elements known as groups or families.

2. How many electron pairs are shared to form a double covalent bond?

A. 1
B. 2
C. 3
D. 4

Correct answer: B

Rationale: The correct answer is B. In a double covalent bond, two pairs of electrons are shared between two atoms. This sharing of two electron pairs results in a stronger bond compared to a single covalent bond where only one pair of electrons is shared. Choice A is incorrect because a single covalent bond involves the sharing of one pair of electrons. Choices C and D are incorrect as they do not represent the correct number of electron pairs shared in a double covalent bond.

3. Which element is considered a noble gas?

A. Oxygen
B. Neon
C. Hydrogen
D. Argon

Correct answer: B

Rationale: The correct answer is 'Neon.' Noble gases are a group of elements with very low reactivity. Neon is one of these elements, known for its stable and unreactive nature. Oxygen, hydrogen, and argon do not belong to the noble gas group. Oxygen is a reactive non-metal, hydrogen is a non-metal and the first element in the periodic table, and argon is a noble gas like neon but not the correct answer in this case.

4. If oxygen is in a compound, what would its oxidation number be?

A. 2
B. -2
C. 0
D. -1

Correct answer: B

Rationale: Oxygen typically has an oxidation number of -2 in compounds because it tends to gain electrons. This is due to its high electronegativity, which leads to oxygen attracting electrons towards itself in a chemical bond. Choice A (2) is incorrect because oxygen doesn't have a +2 oxidation number in compounds. Choice C (0) is incorrect as oxygen rarely has an oxidation number of 0 in compounds. Choice D (-1) is incorrect as oxygen's oxidation number in compounds is typically -2, not -1.

5. If electrons are shared equally in a covalent bond, the bond is classified as what?

A. Polar
B. Non-polar
C. Ionic
D. Hydrogen

Correct answer: B

Rationale: The correct answer is B: Non-polar. In a non-polar covalent bond, electrons are shared equally between the atoms involved, leading to a balanced distribution of charge and no significant difference in electronegativity between the atoms. This equal sharing results in a non-polar bond. Choices A, C, and D are incorrect because a polar bond involves an unequal sharing of electrons, an ionic bond is formed by the transfer of electrons, and a hydrogen bond is a specific type of non-covalent bond.