10th grade atoms, elements and the periodic table

Question 1

Why are gamma rays used to sterilise medical equipment in sealed packs?

• A. They are stopped by plastic
• B. They heat the equipment to 1000 °C
• C. They make the equipment radioactive
• D. They pass through the packaging and kill microbes

Question 2

What is the charge on a calcium ion?

• A. +1
• B. +2
• C. −2
• D. −1

Question 3

An element has two isotopes: mass 77 (10 %) and mass 79 (90 %). What is its relative atomic mass? Give 1 decimal place.

Answer 

Question 4

What are isotopes?

• A. ions with different charges
• B. atoms of the same element with different numbers of neutrons
• C. atoms with different numbers of protons
• D. atoms of different elements with the same mass

Question 5

A sample has an activity of 800 Bq. Its half-life is 12 hours. What is its activity after 36 hours, in Bq?

Answer Bq

Question 6

Calculate the relative formula mass (Mr) of ammonium sulfate, (NH₄)₂SO₄. Relative atomic masses: N = 14, H = 1, S = 32, O = 16.

Answer 

Question 7

A sample contains 12800 undecayed nuclei. How many remain undecayed after 4 half-lives?

Answer 

Question 8

Nuclear radiation: which statement is NOT true?

• A. We can predict exactly when a particular nucleus will decay.
• B. Background radiation comes from natural and man-made sources.
• C. Alpha radiation is the most dangerous if the source is inside the body.
• D. Gamma rays are part of the electromagnetic spectrum.

Question 9

Calculate the relative formula mass (Mr) of CaCO₃. Relative atomic masses: Ca = 40, C = 12, O = 16.

Answer 

Question 10

The count rate of a radioactive source falls from 1600 counts/min to 800 counts/min in 8 minutes. What is its half-life, in minutes?

Answer min

Question 11

Natural copper contains 69 % of mass 63 and 31 % of mass 65. Calculate its relative atomic mass to 1 decimal place.

Answer 

Question 12

Which type of radiation: a fast-moving electron from the nucleus?

• A. alpha (α)
• B. beta (β)
• C. gamma (γ)

Question 13

What is the percentage by mass of oxygen in MgO? Relative atomic masses: Mg = 24, O = 16. Give 1 decimal place.

Answer %

Question 14

Bonding: which statement is NOT true?

• A. In covalent bonds, electrons are transferred from one atom to another.
• B. Simple covalent substances such as water have low melting and boiling points.
• C. Ionic compounds conduct electricity when melted or dissolved.
• D. Ionic compounds have high melting points.

Question 15

What type of bonding is in iron?

• A. ionic
• B. covalent
• C. metallic

Question 16

A factory checks the thickness of paper with radiation passing through it. Which type is best?

• A. beta
• B. gamma
• C. none: radiation cannot pass through paper
• D. alpha