Mystery Solution II

Question 1

What makes the atom unstable?

Answer 1

When atoms do not have full outer shells of electrons

Question 2

What occurs when atoms are unstable?

Answer 2

• Atoms react in a way to try to fill their outer shell
• Through transferring electrons to other atoms by giving up or gaining electrons to complete their outer shell (ionic bonding)
• Or by sharing electrons with other atoms (covalent bonding)

Question 3

What type of element usually form positive ions?

Answer 3

Metallic elements

Question 4

What type of atom usually form negative ions?

Answer 4

Non-metallic elements

Question 5

What are radicals?

Answer 5

When group of atoms are chemically bounded carry a net charge and behave like a single ion

Question 6

Does elements with 4 outer- shell electrons form ions?

Answer 6

No

Question 7

An atom with 7 outer- ring electrons have a valence of -1?

Answer 7

Yes

Question 8

What are valence electrons?

Answer 8

Electrons in the outer shell of an atom

Question 9

What is it when its soluble?

Answer 9

Is when a solid dissolves in a liquid. The resulting solution being clear

Question 10

What is it when its insoluble (precipitate)?

Answer 10

Is when a solid does not dissolve in a liquid. With the resulting solution being cloudy and with the solid dispensed or floating.

Question 11

Why do isotopes have the same chemical properties?

Answer 11

Because they all have the same number of protons and valence electrons hence electron configuration.

Question 12

What is an isotope that is radioactive?

Answer 12

Radioisotope

Question 13

What happens when the number of neutrons is greater than the number of protons?

Answer 13

The nucleus becomes unstable and break up. When this happens a nuclear reaction occurs and the isotopes is said to be radioactive.

Question 14

Who was the early pioneers in radioactivity?

Answer 14

Rutherford: discovers alpha and beta rays
Roentgen: discover x-rays
The Curries: discovers of radium and polonium

Question 15

What does it mean by radioactivity?

Answer 15

Radioactivity is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves.

Basically when an unstable nucleus releases energy to become stable

Question 16

What does alpha, beta, gamma releases?

Answer 16

• Alpha releases alpha particles, neutrons and protons from a nucleus
• Beta releases electrons (beta particles)
• Gamma releases photons, short- wave electromagnetic radiation

Question 17

What is the half- life of a radioactive substance?

Answer 17

Is the time required for one half of it to decay

Question 18

What are sources of radioactivity?

Answer 18

• Primordial: from before the creation of the Earth
• Cosmogenic: formed as a result of cosmic ray interactions
• Human produced: enhanced or formed due to human actions

Question 19

Where are naturally occurring sources of radioactivity?

Answer 19

• Carbon- 14: found in plants and animal tissue

- Potassium- 40: found in minerals and in plants

Question 20

Where are man-made sources of radioactivity used in?

Answer 20

• Certain consumer products e.g. smoke detectors

- Medical purposes with the use of radioactive isotopes

Question 21

What are catalysts?

Answer 21

They speed up reaction and decreases activational energy e.g. enzymes

Though is not used up

Question 22

What phenomenon occurs when a metal ion is heated?

Answer 22

When a metal ion is heated, the electrons get enough energy to jump higher away from the nucleus. And when they fall back, becoming closer to the nucleus they give off this extra energy as light.

Question 23

What is an element?

Answer 23

Substances that contain one type of atom and are pure substances

Question 24

What is a compound?

Answer 24

When different elements are chemically combined together

Question 25

What is a mixture?

Answer 25

Is a substance that contains two or more different substance that are not chemically combined

Question 26

What is valency?

Answer 26

When a charge is possessed by an ion

Question 27

What are the uses of radioisotope Phosphorus -32?

Answer 27

Used to treat leukaemia

Question 28

What are the uses of radioisotope Cobalt- 60?

Answer 28

Used for radiation treatment of cancer

Question 29

What are the uses of radioisotope Carbon -14?

Answer 29

Dating for artifacts

Question 30

What are the disadvantages of nuclear energy?

Answer 30

• There’s no satisfactory ‘safe’ way to dispose the highly radioactive waste due to risk of leakage hence subsequent damage to the environment
• There’s risk of serious accident occurring in nuclear reactors
• E.g. Three Mile Island in the USA 1979
• High cost because with the addition of safety measures in the design compared with a coal burning power station

Question 31

What are endothermic reactions?

Answer 31

The type of reaction which takes in energy e.g. cold packs

Question 32

What is photochemical reactions?

Answer 32

Are endothermic reactions that needs light for them to react

Question 33

What is the reaction rate?

Answer 33

Speed of reaction

Question 34

Why does rate of reaction increases when the temperature increases?

Answer 34

, when heat is applied to a substance the atoms vibrate faster and have a higher likelihood of colliding with other atoms hence the reaction occurs more quickly.

Question 35

Why does the rate or reaction increases when a concentrated acid is added?

Answer 35

Because the particle is able to collide more often hence the rate or reaction increases.

Question 36

Why does the rate of reaction increases when a greater surface area is exposed?

Answer 36

Since there is more of it to react.

Question 37

What are inhibitors?

Answer 37

Substances which slows down reactions