$$60 \times (\frac{1}{2})^4$ = 3.75$$ grams

Question 1

Which subatomic particle is responsible for the identity of an element, and how is this reflected in the periodic table?

Accepted Answer

Protons; the number of protons is the atomic number, which identifies the element.

Question 2

A radioactive isotope of Np-240 has a half-life of 1 hour. If you start with 60 grams, how much will remain after 4 hours?

Accepted Answer

$$60 	imes (\frac{1}{2})^4$ = 3.75$$ grams

Question 3

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

Accepted Answer

A molecule consists of two or more atoms held together by covalent bonds, while a compound consists of two or more elements in a fixed ratio.

Question 4

Which of the following elements is NOT considered one of the four essential elements that make up 96% of living matter?

Accepted Answer

Calcium

Question 5

How many electrons can the first electron shell of an atom hold?

Accepted Answer

2

Question 6

Which type of chemical bond involves the sharing of a pair of valence electrons between two atoms?

Accepted Answer

Covalent bond

Question 7

What is the main difference between polar and nonpolar covalent bonds?

Accepted Answer

Polar bonds have unequal sharing of electrons due to differences in electronegativity, while nonpolar bonds share electrons equally.

Question 8

Which of the following is NOT a property of salts (ionic compounds)?

Accepted Answer

They are considered molecules.

Question 9

What is the electron configuration for a carbon atom?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^2$$

Question 10

Which statement best explains why atoms are electrically neutral?

Accepted Answer

Atoms have the same number of protons and electrons.

Question 11

A hydrogen bond forms when:

Accepted Answer

A hydrogen atom covalently bonded to an electronegative atom is attracted to another electronegative atom.

Question 12

Which of the following best describes van der Waals interactions?

Accepted Answer

They are attractions between molecules due to temporary local charges caused by uneven electron distribution.

Question 13

If an atom has 17 protons, 18 neutrons, and 17 electrons, what is its atomic number and mass number?

Accepted Answer

Atomic number: 17, Mass number: 35

Question 14

Which of the following is a trace element required by humans in less than 0.01% of body mass?

Accepted Answer

Iron

Question 15

What is the result of a chemical reaction reaching equilibrium?

Accepted Answer

The concentrations of reactants and products remain constant, but both forward and reverse reactions continue at equal rates.

Question 16

Which orbital(s) can hold a maximum of 6 electrons?

Accepted Answer

p orbital

Question 17

Which of the following best describes hybridization in the context of molecular shape?

Accepted Answer

The combination and change of s and p orbitals to form new molecular shapes during bonding.

Question 18

Which of the following is true about isotopes?

Accepted Answer

Isotopes of an element have different numbers of neutrons.

Question 19

Which of the following is an example of an ionic bond?

Accepted Answer

The bond between sodium and chlorine in $$NaCl$$

Question 20

Which statement best explains why water molecules are polar?

Accepted Answer

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

Chapter 2: The Chemical Context of Life – General Biology Study Notes

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