Chapter 2.1 and 2.2

What are the three main subatomic particles?

Protons, Neutrons, Electrons

What is the approximate mass of a proton?

~1 amu

What is the approximate mass of a neutron?

~1 amu

What is the approximate mass of an electron?

~0 amu

Which subatomic particles are found in the nucleus?

Protons and neutrons

What determines the atomic number of an atom?

The number of protons

What changes when you change the number of neutrons?

A new isotope is formed

What surrounds the tightly packed nucleus of an atom?

Empty space and a sparse electron cloud

How are electrons arranged?

In shells around the nucleus (K, L, M, N, etc.)

How many electrons can the K shell hold?

2

Which shells have higher binding energy?

Shells closer to the nucleus

When is an atom electrically neutral?

When the number of protons = number of electrons

What is an ion?

An atom with too many or too few electrons (carries a charge)

What is ionization?

The process of removing an electron from an atom

What is an ion pair?

The expelled electron (e-) and the positive ion (cation) formed

Can x-rays ionize atoms?

Yes, they have enough energy to ionize atoms

Formula to calculate the maximum number of electrons in a shell?

2n² (n = shell number)

How many electrons can the N shell hold?

32 (2 × 4²)

What is the maximum number of electrons in the outermost shell?

8 (valence electrons)

What determines the group number in the periodic table?

Number of valence electrons

What determines the period number in the periodic table?

Number of electron shells

What two forces hold electrons in orbit around the nucleus?

Centripetal force (pull of nucleus) and Centrifugal force (electron speed)

What happens to binding energy as electrons get closer to the nucleus?

It increases

What does Eb stand for?

Binding energy

What must incoming radiation exceed to ionize an atom?

The binding energy (ionization potential)

In carbon, the L shell has a binding energy of 10 eV. How much is required to ionize it?

34 eV

What happens if radiation energy is less than the ionization potential?

Heat is produced

What is the chemical symbol of an element called?

X

What is the atomic number (Z)?

Number of protons

What is the atomic mass number (A)?

Protons + Neutrons

Is atomic mass number the same as atomic mass?

No, atomic mass is more precise

What are isotopes?

Atoms with the same number of protons but different numbers of neutrons

What are isobars?

Atoms with the same number of nucleons but different numbers of protons and neutrons (different elements)

What are isotones?

Atoms with the same number of neutrons but different numbers of protons (different elements)

What are isomers?

Identical atoms that exist at different energy states (metastable states)

What indicates a metastable state?

An “m” after the element (ex. Technetium-99m)

What do atoms combine to form?

Molecules

Give an example of a molecular equation.

2H₂ + O₂ → 2H₂O

What is an ionic bond?

Attraction between two oppositely charged ions

What is a covalent bond?

Sharing of electrons between atoms

What are unstable atoms called?

Radionuclides

What is radioactive decay?

Spontaneous emission of radiation from unstable atoms

What does “radioactive” mean?

Actively emitting radiation

What are radioisotopes?

Isotopes that are unstable due to too many or too few neutrons

What are the two main types of radioactive decay?

Alpha emission and Beta emission

What happens in alpha emission?

2 protons and 2 neutrons are emitted, changing the element

What happens in beta emission?

A neutron converts into a proton and an electron is ejected, changing the element

What is half-life (T½)?

Time it takes for half of a radioactive sample to decay

If I-131 has a half-life of 4 days, how much of an 8g sample remains after 16 days?

0.5 g

What are the two main types of ionizing radiation?

Particulate and Electromagnetic

What are particulate radiations made of?

Matter (alpha and beta particles)

What are electromagnetic radiations made of?

Energy (gamma rays and x-rays)

What is an alpha particle?

A helium atom with no electrons, very ionizing

What is a beta particle?

An electron or positron, moderately ionizing

What is a gamma ray?

High-energy radiation from the nucleus, highly penetrating

What is an x-ray?

High-energy radiation from outside the nucleus, highly penetrating

How many groups are elements arranged into on the periodic table?

Eight groups

What is the smallest particle of an element?

Atom

What is the smallest particle of a compound?

Molecule

What is a molecule?

Atoms of various elements combined into a structure

What is a chemical compound?

Any quantity of one type of molecule

What keeps an electron in orbit around the nucleus?

Centripetal force

Can any outer shell hold more than eight electrons?

No, maximum is 8

Are the atomic mass number and the precise mass of an atom equal?

No, they are not equal

What is radioactivity?

Spontaneous emission of particles and energy to become stable

What are the main emissions from radioactive decay?

Alpha particles, Beta particles, and usually Gamma rays

What is an alpha particle?

A helium nucleus with 2 protons and 2 neutrons

What is a beta particle?

An electron emitted from the nucleus of a radioactive atom

Where do gamma rays originate from?

The nucleus

Where do x-rays originate from?

The electron cloud

What is radioactive half-life?

Time required for radioactivity to be reduced to one-half its original value

How many half-lives equal one tenth-life?

3.3 half-lives

What is the formula for activity remaining in radioactive decay?

Activity remaining = Original activity × (0.5)^n

In the decay formula, what does n represent?

Number of radioactive half-lives