The Atom Flashcards
An atom consists of
- Nucleus containing protons & neutrons (together nucleons)
- A cloud of electrons surrounding the nucleus
Protons and neutrons are held together by
A force called the nuclear force
Mass of an atom is concentrated in
The nucleus
The electrons orbital region accounts for
Most of the volume of the atom
Protons charge
Positive
Electrons charge
Negative
Neutrons charge
No charge
The atom as a whole charge
Neutral
If an atom loses/gains electrons it becomes
Charged (called an ion)
The atomic number symbol
Z
The mass number symbol
A
No. of neutrons can be calculated as
A-Z
Nuclear notations
Atomic number at the bottom, Mass number at the top
Number of protons in an atom of an element cannot change because
It determines the properties of the element and it completely defines which element you have
In a naturally occurring sample of an element some atoms have different
Mass numbers: this difference is due to some atoms having different number of neutrons in the nucleus
The periodic table is arranged in order of
increasing atomic number (number of protons and electrons)
Group 1
Alkali metals
Group 2
Alkali earth metals
Group 17
Halogens
Group 18
Noble gases/inert gases
Group 2-13
Transition elements
Metalloids
B, Si, Ge, As, Sb, Te
Gases
O, N, F, Cl, H
Liquids at room temperature
Br and Hg
All other elements are
Solids at room temperature
The chemical properties of an element are determined by the
Electron arrangement: because it is the electrons which interact when atoms combine to form compounds during a chemical reaction
Electrons being around
The outside can interact unlike nuclei
Valence electrons
Are those which interact during chemical bonding
The Aufbau principle describes how
- Electrons are arranged in orbitals
- The order in which electrons fill up orbitals
- Pauli Exclusion Principle
- Hund’s Rule
- An energy level is full when each orbital contains 2 electrons
- S and p are ‘sub-levels’
Pauli Exclusion Principle
An orbital an contain a maximum of 2 electrons provided they have an opposite spin (using up/down arrows)
Hund’s Rule
When assigning electrons to p-orbitals, each p-orbital must contain one electron before pairing can take place
Metals on LHS
Lose electrons to form Cations
Non-metals on RHS
Gain electrons to form Anions
Noble gases have
A very stable full outer energy level. Electron arrangement is very stable which is why noble gases do not react
Atoms form ions to become
More stable (energetically favourable): they do this by losing or gaining electrons to achieve a noble gas electronic structure
