Week 2: Atomic Number and Atomic Mass Flashcards
What is Atomic Mass?
Protons + Neutrons
What is Atomic Number?
Number of protons (same as electrons unless an ion)
What are isoptopes?
Same element with a different number of neutrons and therefore different atomic mass.
Why can the periodic table show an element with a decimal as it’s atomic mass?
An average is taken of all possible isotopes present on Earth.
What is the equation for relative isotopic mass?
Σ (Isotopic Mass x Abundance (%) ) / 100 (Total Abundance)
Which atoms are stable?
Atoms with a full outer shell.
What does the chemical properties of substances elements rely on?
How many electrons are present in their outer shell.
Which groups are metals?
Group 1 and 2
What are cations?
Ions with a positive charge (Group 1 and 2 ions)
Which groups are non-metals?
Group 6 and 7
What are anions?
Ions with a negative charge
What was Bohr’s Atomic Model?
The first model proposing that electrons were not found at random in the atom but at certain distances from the nucleus, arranged in shells.
Features of his model include:
- Each shell of electrons is at a definite radius from the nucleus.
- The electrons in each shell have equal energy.
- Shells further from the nucleus are higher energy than those closer.
- Electrons occupy the lowest energy shell possible.
What are nucleons?
The particles which make up the nucleus.
Which two particles are the nucleons?
Proton and Neutron
What is the relative mass and relative charge of a proton?
RM = 1
RC = +1
What is the relative mass and relative charge of a neutron?
RM = 1
RC = 0
What is the relative mass and relative charge of an electron?
RM = Negligible (1/1840)
RC = -1
What are sublevels Why are they important?
- Within the shells/energy levels of the Bohr model, there are sublevels.
- Here, electrons have small but significant differences in energy.
- They help to explain the chemistry of many elements and compounds.
What are the four sublevels?
s, p, d, f
How many electrons does the s sublevel contain?
2
How many electrons does the p sublevel contain
6
How many electrons does the d sublevel contain?
10
How many electrons does the f sublevel contain?
14
What are orbitals?
- Electrons exist as orbitals.
- These are volumes where the electron is likely to be found as they are too small to pin down very accurately and have the characteristics of a wave which makes their exact position hard to pin know.
(Different to Bohr’s model which has electrons at a certain radii)
How many electrons can an orbital hold?
2
(Therefore s = 1 orbital, p = 3 orbitals etc.)
Do orbitals have identical energy levels?
- If they are in the same sublevel, yes.
- s < p < d < f
What is Hund’s rule?
Electrons go into the p orbitals separately rather than pairing up in a single orbital.
