Mass Defect & Nuclear Stability/Synthesis (8/25)

Which two people arranged the periodic table by atomic weight?

Mendeleev and Meyer

How is the periodic table arranged now?

By atomic number - correlated to atomic weight

What is a row in the periodic table called?

Period

What is a column in the periodic table called?

Family/Group

What is the accepted definition for transition metals?

Elements where the neutral / Oxidation states have a partially filled d orbital (why group 3 and 11 don’t really count)

What is the family name for Group 1 elements?

Alkali metals

What is the family name for Group 2 elements?

Alkali Earth metals

What is the family name for Group 15 elements?

Pnictogens

What is the family name for Group 16 elements?

Chalcogens

What is the family name for Group 17 elements?

Halogens

What is the family name for Group 18 elements?

Noble gases

What is the big bang?

Tiny atom expands and cools → entire universe is created

What temperature did the big bang have to cool to to start forming protons and neutrons?

10^10 K

What is pair creation?

2 gamma ray photons colliding to become a proton and anti-proton

What is pair annihilation?

An anti-proton and proton colliding to become two gamma ray photons

At what temperature is there not enough energy for pair production?

6 * 10^9 K

How are deuterium nuclei formed?

Protons and neutrons combine

What is nucleosynthesis?

The formation of nuclei

What four elements did the first nucleosynthesis form?

H, He, Li, B (first four)

Why are more elements able to form?

Matter starts to dominate as the temperature cools; becomes “transparent” → formation of stars

What is the importance of stars?

They throw out new atoms

What are Coulombic forces?

The forces that state that less distance = more repulsion

At very short distances, what forces overcome Coulombic forces?

nuclear force → formation of nuclei

What are magic numbers?

An ideal number of protons or neutrons for a completed shell.

List the magic numbers for protons & neutrons.

2, 8, 20, 28, 50, 82, 114, and 126

How many protons / neutrons do most stable nuclei have?

An even number

What ratio do stable nuclei depend on?

Protons : Neutrons

No stable nuclei exist above _ atomic number

82

As the atomic number increases, there are usually more ___. This results in ___.

neutrons; high n:p ratio

What are the two unstable nuclei in nuclei with atomic numbers below 83?

Pm,Tc

What universal law does not apply to atoms?

conservation of mass

What is mass defect?

In atoms, sum of parts > total atom The difference is mass defect

What is the significance of mass defect?

The higher this difference is, the more stable the nucleus is.

What is a nucleon?

proton or neutron; piece of a nucleus

With what equation can you calculate mass defect?

E = mc^2

m = mass defect

c = speed of light

E = binding energy

What do atoms with higher nucleons have a tendency to do?

Split / decay (radioactivity)

What is nuclear fission?

Spontaneous splitting of nuclei

What is SATP?

standard ambient temperature and pressure

What are the conditions of SATP?

25*C, 100 kPa

What two elements exist as liquids in SATP?

Br, Hg

How many elements exist as gases under SATP?

11

What are the qualifications to be a metal?

• luster

• good heat conductor

• ductile

• high 3D electrical conductivity at SATP

What two nonmetals have luster? Why does this matter?

Iodine, silicon

Luster can’t be the only qualification

What nonmetal is a good heat conductor? Why does this matter?

Diamond

Heat conducting can’t be the only qualification

What metals aren’t ductile? Why does this matter?

Some transition metals

Ductility can’t be the only qualification

What is the best single qualifier to be a metal?

high 3D electrical conductivity at SATP

Why does pressure matter when defining a metal?

Iodine (nonmetal) is a good conductor at high pressure

Why does temperature matter when defining a metal?

Below 18*, Tin becomes a semiconductor

As temperature rises, what happens to conductivity in metals?

Lower conductivity

What is Periodic Law?

Existence of some periodic properties

What periodic property doesn’t really exist in quantum mechanics?

Atomic radii because of not being able to have clearly defined atomic orbitals

What are the three different forms of atomic radii?

Covalent, Van Der Waals, metallic

How do you calculate covalent radii?

1/2 * (distance between nuclei at a single bond)

How do you calculate Van Der Waals radii?

1/2 * (distance between nuclei of a non-bonded molec)

How do you calculate Metallic radii?

1/2 * (distance between nuclei of atoms in a metallic structure)

General periodic trend for atomic radii

Decreasing from left to right; increasing from up to down (opposite of electronegativity)