Learning Objectives Flashcards
What is an atom made up of?
Electrons, protons and neutrons
What is the relative mass and charge of a proton, neutron and electron respectively?
Proton: 1 and +1
Neutron: 1 and 0
Electron: 1/1840 and -1
What is the atomic number and what is the mass number?
The atomic number is the number of protons in the nucleus
The mass number is the number of protons and neutrons in the nucleus
How do you find the number of sub atomic particles in an atom or ion?
Look at the periodic table, there will be equal numbers of protons and electrons for a neutral charge
If it’s a ion, depending on if it is positive or negative there will be less or more electrons
What are isotopes?
Atoms of an element with the same number of protons and different number of neutrons
What is relative isotopic mass?
The mass of an atom of an isotope compared to 1/12th of the mass of a C-12 atom
What is relative atomic mass?
The average mass of an atom compared to 1/12th of the mass of a C-12 atom
How is relative molecular mass different from relative formula mass?
molecular mass is the mr so is for covalent compounds
formula mass is for ionic compounds bc they are not molecules
How do you calculate relative molecular mass AND relative formula mass (Mr) from relative atomic mass?
Add up all of the relative atomic masses in the molecule
- (relative atomic mass x amount of that element) + … etc.
How do you calculate the relative atomic mass?
total mass of all atoms / total number of atoms
How to do you calculate relative atomic mass when given percentage abundances?
(percentage x mass) + (percentage x mass) etc..
e.g. Mg contains 50% of Mg-24 and Mg-25
- (0.5 x 24)+(0.5 x 25)
How can a mass spec graph be used to find the Mr?
The peak with the highest m/z value (NOT M+1) corresponds to the Mr, aka the right most peak
What is the first ionisation energy?
The energy required to remove one mole of electrons from one mole of atoms in the gaseous state to produce one mole of 1+ ions
What are successive ionisation energies?
The energy required to remove electrons one after the other
What is the ionisation energy effected by and why?
- Number of protons which increases the ionisation energy because the electron and positive nucleus will have stronger electrostatic forces of attraction resulting in more energy required to remove an electron
- Shielding which decreases the ionisation energy as the outermost electron will be further from the positive nucleus with more shielding resulting in weaker electrostatic forces so less energy is required to remove the electron
- Electron sub-shell from which the electron is removed, this is because different subshells have different shapes and so the electrons fly farther in some than other so less energy will be needed to remove and electron (electrons get farther in p orbitals than s orbitals)
What is the pattern of first ionisation energies across a period?
The energies will generally increase as:
The nuclear charge increases
The shielding remains the same
What is the pattern of first ionisation energies down a group
It will decrease down a group as:
The increase in shielding outweighs the increase in nuclear charge, meaning there are less attractive forces between the nucleus and the outermost electron, so less energy is required to remove it
How does atomic emission spectra provide evidence for quantum shells?
The data appears as a line spectrum rather than being continuous, showing that electrons can only be at specific energy levels and jump between them evidencing quantum shells.
Also each element will have a unique spectra due to each’s unique arrangement of electron energy levels
How do successive ionisation energies evidence the existence of quantum shells?
It shows that significant jumps in energy are required for an electron to move to another shell
