Q: Which equation correctly calculates the relative atomic mass (RAM) of an element from its isotopes?

$$\text{RAM} = \frac{(\text{mass of isotope A} \times \% \text{of isotope A}) + (\text{mass of isotope B} \times \% \text{of isotope B})}{100}$$

Question 1

Which statement best explains why atoms contain equal numbers of protons and electrons?

Accepted Answer

Because atoms are neutral, and the positive charge of protons cancels the negative charge of electrons.

Question 2

Which subatomic particle has a relative mass of approximately $$\frac{1}{1836}$$?

Accepted Answer

Electron

Question 3

Most of the mass of an atom is concentrated in which part?

Accepted Answer

The nucleus

Question 4

Which scientist's experiment led to the conclusion that the atom is mostly empty space with a dense nucleus?

Accepted Answer

Ernest Rutherford

Question 5

What is the meaning of the term 'mass number' of an atom?

Accepted Answer

The total number of protons and neutrons in the atom

Question 6

Isotopes of an element have:

Accepted Answer

The same number of protons but different numbers of neutrons

Question 7

Given an atom with atomic number $$Z = 17$$ and mass number $$A = 35$$, how many neutrons does it have?

Accepted Answer

18

Question 8

A sample of chlorine contains 75% chlorine-35 and 25% chlorine-37. What is the relative atomic mass (RAM) of chlorine in the sample?

Accepted Answer

$$35.5$$

Question 9

Which equation correctly calculates the relative atomic mass (RAM) of an element from its isotopes?

Accepted Answer

$$	ext{RAM} = \frac{(	ext{mass of isotope A} 	imes \% 	ext{of isotope A}) + (	ext{mass of isotope B} 	imes \% 	ext{of isotope B})}{100}$$

Question 10

Which of the following best describes the nucleus of an atom?

Accepted Answer

It is very small compared to the overall size of the atom and contains protons and neutrons.

Question 11

If an atom has 12 protons, 12 neutrons, and 12 electrons, what is its mass number?

Accepted Answer

$$24$$

Question 12

Why are the relative atomic masses of some elements not whole numbers?

Accepted Answer

Because elements are mixtures of isotopes with different masses.

Question 13

Which model of the atom was described as 'plum pudding'?

Accepted Answer

Thomson's model

Question 14

An atom of sodium has atomic number $$11$$ and mass number $$23. $$How many electrons does a neutral sodium atom have?

Accepted Answer

11

Question 15

Which statement is true about atoms of the same element?

Accepted Answer

They always have the same number of protons.

Question 16

A neutral atom of carbon has atomic number $$6$$ and mass number $$12. $$What is the number of neutrons in this atom?

Accepted Answer

6

Question 17

Which of the following is a correct statement about electrons in an atom?

Accepted Answer

Electrons are found in shells surrounding the nucleus.

Question 18

If an atom has 20 protons, 22 neutrons, and 20 electrons, what is its atomic number and mass number?

Accepted Answer

Atomic number $$= 20$$, mass number $$= 42$$

Question 19

Which of the following best explains why the atomic number is unique to each element?

Accepted Answer

Because it represents the number of protons in the atom.

Question 20

A hospital uses a sample of oxygen gas containing two isotopes: oxygen-16 (99.76%) and oxygen-18 (0.20%). What is the approximate relative atomic mass of oxygen in this sample?

Accepted Answer

$$16.00$$

Atomic Structure: Key Concepts in Chemistry (Edexcel GCSE Chemistry)

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