11th Chemistry - Unit 2 (Chpt 4 & 5) review

Question 0

What is gamma radiation?

Answer 0

• Most harmful radiation as it can penetrate lead or concrete.
• high energy radiation. Kills living cells
• No mass, neutral charge

Question 1

What are alpha and beta decay?

Answer 1

Alpha
- least harmful. Stopped by paper or clothing
- 2 protons/2 neutrons. Charge of +2
- appreciable mass
Beta
- more harmful.  Stopped by metal foil
- high speed electrons
- found/named by Rutherford
- violates law of conservation of energy

Question 2

What did John Dalton discover? How did he discover it?

Answer 2

Dalton

• elements can only combine atomically when they are in fixed ratios
• did numerous experiments to measure chemical reactions and determined mass ratios

Question 3

What did J.J. Thomson discover? How did he discover it?

Answer 3

JJ Thomson

• electron. Negatively charged
• used ray tubes to ID electrons.
• determined ratio of electron mass to its charge
• Plum pudding model

Question 4

What did Ernest Rutherford discover? How did he make this discovery?

Answer 4

Rutherford

• small positive nucleus in atoms
• repels positive alpha particles
• used gold foil and shot alpha particles at it
• nuclear atomic model

Question 5

What is the basic structure of an atom?

What are the differences in a neutral atom, ion and isotope?

Answer 5

Atom - protons & neutrons in nucleus. Electrons orbiting nucleus
Neutron - large, no charge
Proton - large, positive charge
Electron - small, negative charge

Neutral - protons = electrons. No charge
Ion = less or extra electrons resulting in + or (-) charge
Isotope - extra neutron increasing atomic mass

Question 6

Draw and discuss the Bohr model

Answer 6

If neutral - Protons = Atomic # = Electrons

Neutrons may be different.

Protons & Neutrons in nucleus of picture

Electrons orbit nucleus in rings.
Each ring holds 2n^2. Ring 1 -2
Ring 2 - 8
Ring 3 - 18

Question 7

What is the difference between radioactivity and nuclear reactions?

Answer 7

Radioactivity - substances spontaneously emit radiation

Nuclear reactions - involve change in the nucleus of the atom

Question 8

Explain radioactive decay

Answer 8

• Spontaneous process

- unstable nuclei lose energy by emitting radiation

Question 9

What is meant by nuclear stability?

Answer 9

Atoms with either too many or too few neutrons lose energy through decay to form a stable nucleus where neutrons = protons

Question 10

T/F

Number of protons AND number of neutrons remain the same for all isotopes of the same element

Answer 10

False.

Change in neutrons is what makes it an isotope

Question 11

T/F

The number of protons AND the mass number determine the type of atom

Answer 11

True.
As # of protons change the element changes.
Change in mass number indicates change in either protons or neutrons which also changes

Question 12

T/F

Chemical reactions involve changes in the number of electrons

Answer 12

True.

Pulled away and combined with other elements.

Question 13

T/F

Nuclear reactions involve changes in the electrons.

Answer 13

False
NUCLEAR reactions involve changes in the
NUCLEUS

Question 14

What are the charges in these types of
radiation?

Alpha
Beta
Gamma

Answer 14

Alpha 2+
Beta. 1(-)
Gamma. No charge

Question 15

What determines the stability of an atom?

Answer 15

Neutron to proton ratio

Question 16

What is the maximum number of electrons that can be present in each principal energy level?
A. n
B. n^2
C. 2n
D. 2n^2

Answer 16

D. 2n^2

Question 17

What is the lowest state of an atom called?

A. ground state
B. excited state
C. California
D. state of flux

Answer 17

Ground state. 2n^2 or only 2 electrons

Question 18

Element Q has isotopes Q248, Q252, and Q259. If the atomic mass of element Q is 258.63, which isotope is most abundant?
A. Q248
B. Q252
C. Q259
D. Cannot be determined with the given information

Answer 18

C. Q259. skews average up

Question 19

Iodine-131 undergoes radioactive decay and forms an isotope with 54 protons and 77 neutrons. What type of decay occurs in this isotype? How can you tell?

Answer 19

Gamma rays?? No change in charge?

Question 20

An element has three naturally occurring isotopes. What additional information do you need to compute it’s atomic mass?

Answer 20

The abundance of each isotope

Question 21

Why are some atoms radioactive?

Answer 21

neutron to protron ratio is either too little or too much

Question 22

Discuss how radioactive atoms gain stability

Answer 22

Radioactive decay - emit alpha & beta particles until neutron to protron ratio allows stability

Question 23

What particles account for most of an atom’s mass?

Answer 23

protons and neutrons

Question 24

``` What is the primary factor in determining an atom's stability? A. neutron to proton ratio B. protron to electron ratio C. neutron to electron ratio D. alpha particle to beta particle ratio ```

Answer 24

A. neutron to proton ratio

Question 25

Classify each of the following as a chemical reaction, nuclear reaction or neither A. Thorium emits a beta particle B. Two atoms share electrons to form a bond C. A sample of pure sulfur emits heat energy as it slowly cools D. A piece of iron rusts

Answer 25

A. Beta particles - radioactive B. Ionic bond - chemical C. Neither. Change of state only D. Rust - chemical