Avg Atomic Mass and Radiation Decay

Question 1

What is the mass number?

Answer 1

of protons and neutrons

Question 2

How much do a proton and a neutron weigh?

Answer 2

1 amu

Question 3

Why do we not concern ourselves with the mass of electrons when determining the weight of an atom?

Answer 3

Their mass is barely anything

Question 4

Ho do we name the isotope of Boron that has 5 neutrons?

Answer 4

Boron-10
B-10

Question 5

Why can’t we use a regular average to determine the average mass of a boron atom?

Answer 5

Boron exists as a mixture of isotopes with different masses and abundances, so a weighted average must be used instead.

Question 6

How do you change a percent into a decimal?

Answer 6

divide the percentage by 100 or simply move the decimal point two places to the left.

Question 7

Why didn’t Mr. DeWitt’s first weighted average of copper match the average atomic mass on the periodic table?

Answer 7

he may not have used the correct relative abundances or isotope masses that reflect the natural occurrence of copper isotopes…..or he rounded the numbers

Question 8

What is the difference between mass number and atomic number?

Answer 8

The atomic number is the number of protons in an atom’s nucleus, while the mass number is the total number of protons and neutrons combined.

Question 9

While most atoms are stable, some are ____ which means that they have a tendency to undergo spontaneous _____ _____.

Answer 9

• Radioactive
• Nuclear Decay

Question 10

What is an alpha particle made of?

Answer 10

two protons and two neutrons, which is the same as a helium nucleus.

Question 11

What else is emitted from the nucleus during alpha decay?

Answer 11

energy in the form of radiation is also emitted from the nucleus (Gamma rays)

Question 12

What is an alpha particle?

Answer 12

positively charged particle consisting of two protons and two neutrons, identical to the nucleus of a helium atom.

Question 13

Who coined the term radioactivity?

Answer 13

Marie Curie

Question 14

How does the emission of an alpha particle affect the atomic number and the mass number?

Answer 14

• decreases the atomic number by 2 (since 2 protons are lost)
• decreases the mass number by 4 (since 2 protons and 2 neutrons are lost)

Question 15

What is a beta particle?

Answer 15

a high-energy, high-speed electron emitted from the nucleus during beta decay, when a neutron converts into a proton or vice versa

Question 16

How does the emission of a beta particle affect the atomic number and the mass number?

Answer 16

• increases the atomic number by 1 (if it’s a beta-minus decay, where a neutron turns into a proton)
• does not change the mass number, as the total number of protons and neutrons remains the same.

Question 17

Why do the three types of radiation respond to a electric/magnetic field differently?

Answer 17

• alpha particles are positively charged
• beta particles are negatively charged
• gamma rays have no charge,
• this causes alpha and beta particles to be deflected in opposite directions while gamma rays remain unaffected.

Question 18

What are gamma rays?

Answer 18

high-energy electromagnetic radiation emitted from the nucleus during radioactive decay, with no mass or charge, making them the most penetrating form of radiation

Question 19

When does gamma emission usually occur?

Answer 19

after alpha or beta decay, when the nucleus is left in an excited energy state and releases excess energy in the form of gamma rays to become more stable

Question 20

What is a half-life, t_1/2?

Answer 20

time it takes for half of the atoms in a radioactive substance to decay into a more stable form

OR

time required for 1/2 of the nuclei in a radioisotope sample to decay into its products