$$2n^2$$ where $$n=2$$, so $$2 \times 2^2$ = 8$$ electrons

Question 1

Which of the following statements best explains why oxygen is more electronegative than hydrogen?

Accepted Answer

Oxygen has more protons, which increases its ability to attract electrons.

Question 2

A neutral atom of sodium ($$\mathrm{Na}) $$has an atomic number of 11 and an atomic mass of 23. How many neutrons does it have?

Accepted Answer

$$23 - 11 = 12$$ neutrons

Question 3

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed when two atoms share electrons.

Question 4

What is the maximum number of electrons that can occupy the second electron shell of an atom?

Accepted Answer

$$2n^2$$ where $$n=2$$, so $$2 	imes 2^2$ = 8$$ electrons

Question 5

Which of the following is a trace element essential for life, found in small amounts in living organisms?

Accepted Answer

Iron (Fe)

Question 6

A radioactive isotope has a half-life of 10 years. If you start with 100 grams, how much will remain after 30 years?

Accepted Answer

$$100 \div 2^3$ = 12.5$$ grams

Question 7

Which of the following best describes the difference between a molecule and a compound?

Accepted Answer

A molecule is two or more atoms bonded together, while a compound is two or more different elements bonded together.

Question 8

Which of the following atoms is most likely to form a cation?

Accepted Answer

An atom that loses an electron during a chemical reaction.

Question 9

Which statement about hydrogen bonds is correct?

Accepted Answer

They are weak individually but collectively can be strong.

Question 10

Which of the following best explains why water is a polar molecule?

Accepted Answer

Oxygen is more electronegative than hydrogen, causing unequal sharing of electrons.

Question 11

If an atom has 8 protons, 8 neutrons, and 10 electrons, what is its net charge?

Accepted Answer

$$8$$ protons $$- 10$$ electrons $$= -2 ($$net charge of $$-2)$$

Question 12

Which of the following is true about isotopes?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 13

Which of the following elements is NOT one of the main elements found in living organisms (CHONPS)?

Accepted Answer

Calcium (Ca)

Question 14

Which of the following best describes ionic bonding?

Accepted Answer

A bond formed by the complete transfer of electrons from one atom to another.

Question 15

Which of the following statements about the octet rule is correct?

Accepted Answer

Atoms are more stable when their valence shell is full.

Question 16

Which of the following is the correct formula for calculating the atomic mass of an atom?

Accepted Answer

$$	ext{Atomic mass} = 	ext{Number of protons} + 	ext{Number of neutrons}$$

Question 17

Which of the following best explains why radioactive isotopes are useful in dating fossils?

Accepted Answer

They emit energy at a predictable rate, allowing calculation of age based on half-life.

Question 18

Which of the following is true about valence electrons?

Accepted Answer

They are found in the outermost shell and determine chemical reactivity.

Question 19

Which of the following scenarios would most likely result in the formation of a polar covalent bond?

Accepted Answer

Two atoms with significantly different electronegativities share electrons.

Question 20

Which of the following is a correct statement about anions?

Accepted Answer

Anions are negatively charged ions due to the gain of an electron.

Chapter 2: The Chemical Context of Life – Study Notes

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