Atomic Structure Intro Flashcards
Describe a pure substance
- has constant properties and composition aka. made of one type of atom
- all matter can be separated into pure substances
- they can be elements or compounds and are changed via chemical reactions
What is the law of definite proportions?
Law that a chemical compound maintains at a fixed ration regardless of source or amount
What is the law of multiple proportions?
The law that when 2 elements combine, the ratio of the 1 element that combines with the fixed weight of the element are whole numbers.
Isotope
Atoms of same element with different mass no.
Atomic number
- Number of protons (= number of electrons)
- Bottom number for element on periodic table
Mass number
- Number of protons and neutrons combined
- Top number for element on periodic table
What is a unit of mass
It is 1/12th of carbon 12 (also called Dalton/D1)
What is relative atomic mass
It is the ratio of the mass of one atom of an element against the mass of 1/12th of an atom of carbon 12
What is relative molecular mass?
The ratio of the average mass of a molecule to the mass of one 1/12th of an atom of carbon 12
What is Avogrado’s constant?
The number of atoms in 12g of carbon 12
6.022045 10^23/mol
What is molar mass (and equation)
Molar mass = grams/mole
- sum of the total mass in grams of all the atoms that make up a mole of particular molecule
What is electronegativity? (Describe)
- Tendency of an atom to attract a pair of shared electrons
- happens for covalent bonds
- affected by atomic number and the distance of the valence bonds from the nucleus
Homonuclear
Multiple molecules of the same element
Heteronuclear
Multiple of molecules of different elements
Disassociation energy
Energy required to fracture a bond between atoms
What are the 3 different electronegativity scales
Pauling scale = mean difference between average disassociation energies homo and heteronuclear compounds of an element
Alfred- Rochow = value of electrostatic force exerted by nuclear charge of valence electrons
Mullikan - average ionisation energy and electron affinity of element
Describe an atom
- nucleus positively charged and consists of protons (+) and neutrons (0)
- shells negatively charged and consist of electrons (-)
- shells 100,000 times larger than nucleus
- nucleus contains 99.9% of mass
Describe how periodic table can be used to observe ionisation
- Increases across periods as energy also increases to remove electron and atomic radius decreases = greater attraction between electrons and nuclei
- Decreases as atomic number increases/down a group
- noble gasses don’t want to react = least likely to ionise
Describe relationship between periodic table and electron affinity
- increases across periods
- sometimes decreases down a group
- low for noble elements
Describe electron shells and sub shells
- shells are discrete (not in between energy transitions)
- shells contain max 2n^2 electrons
- shells divide into sub shells S (2 electrons), P (6), D (10), F (14)
- mains shell 1 = 1s (2 electrons)
- mains shells 2 = 1s and 1p (8 electrons)
- mains shell 3 = 1p and 1 d (18 electrons)
- s shells spherical
- p shells figure of 8
Describe electron orbitals
- function probabilities (95%) of electron being present
- no of sub shells reflect spatial orientation
Describe energy levels of electrons
divided into 4 quantum numbers, electrons will differ in at least 1 of them:
- principle quantum number, n (size of orbitals)
- angular quantum number, l (shape of orbitals)
- magnetic quantum number, m (orientation of orbitals)
- spin quantum number, s ( all electrons need different spins.. spins clockwise on axis = spin up, counterclockwise = spin down) if spins unpaired = reactivity
How to work the relative atomic mass
Add together the mass number of each element
How to work out molecular mass
- Determine molecular formula
- Find atomic mass of each element
- Multiple atomic mass by number of that element in the molecule
- Add values together
How to work out the number of moles
Number of moles = mass x relative molecular mass
Molar concentration/molarity
Number of moles of a solute that can dissolve in 1 litre of solution
Molarity equation
Amount of solute (in moles) / volume of solution (L)
