GCSE Atomic Structure & Periodic Table 2

Question 1

An element has 17 protons and 18 neutrons. What is its mass number?

Accepted Answer

35

Answer

Mass number = protons + neutrons = 17 + 18 = 35.

Question 2

Which of the following best describes isotopes of the same element?

Accepted Answer

Same atomic number, different number of neutrons

Answer

Isotopes have the same atomic number (protons) but differ in neutron count, giving different mass numbers.

Question 3

In the modern periodic table, elements are arranged in order of increasing:

Accepted Answer

Atomic number

Answer

Mendeleev used atomic mass, but the modern periodic table orders elements by atomic number (number of protons).

Question 4

Which subatomic particle determines the chemical properties of an element?

Accepted Answer

Electrons

Answer

Electrons, especially the outermost shell electrons, determine how an element reacts chemically.

Question 5

Sodium has atomic number 11. How many electron shells does a sodium atom have?

Accepted Answer

3

Answer

Sodium's electron configuration is 2,8,1 — filling three shells.

GCSE - General Certificate of Secondary Education Practice Test