CH2 Elements And The Periodic Table Flashcards
(19 cards)
Element
Materials containing just one type of atom. 118 types , 98 found in nature
Electrons
Negatively charged particles
The nucleus
The nucleus of an atom is approximately 10,000-100,000 times smaller than the size of an atom. The subatomic particles in the nucleus are the protons and neutrons called nucleons
Isotopes
Atoms of the same element that contain the same number of protons but different number of neutrons. Atomic number remains the same, Mass number is different
Ions
Atoms which have lost or gained electrons, creating negative or positive charge
Anion
Gained electrons = negative charge (-2)
Cation
Lost electrons + positive charge (2+)
Emission spectra
When atoms are heated, they give off electromagnetic radiation or light. If the lines are passed through a prism it produces a spectrum with a number of coloured lines known as an emission spectra. Each element has a unique emission spectra
the Bohr model
- electrons revolve around the nucleus in fixed, circular orbits
- these orbits correspond to specific energy levels in the atom
- electrons can only occupy fixed energy levels and cannot exist between two energy levels.
- orbits of larger radii correspond to energy levels of higher energy
Electron shells (Bohr)
The Bohr model of the atom proposes that electrons are grouped into different energy levels called shells, n=1, 2, 3, 4…
Max number of electrons held in a shell
2n^2
Why Schrödinger not Bohr
The Bohr model cannot accurately predict the emission spectra of atoms with more than one electron
It is unable to explain why electron shells can only hold 2n^2 electrons
Doesn’t explain why the fourth shell accepts the two electrons before the third shell is completely full.
The Schrödinger model
In this model, the electrons occupy. Three dimensional space around the nucleus known as an orbital
Conclusions of the Schrödinger
There are major energy shells in an atom that are called shells
- these shells contain seperate energy levels of similar energy called sub shells, which are labelled s, p, d, f. Each sub shells can only hold a. Certain number of electrons.
Groups - vertical columns
For main group elements the group number can be used to determine the number of valence electrons
- the valence electrons determine the physical properties of the atom
- elements in the same group have similar physical properties
Periods - horizontal rows
The period an element is located in is equal to the number of occupied electron shells in the elements atoms.
Blocks
The blocs in the periodic table contain elements that have the same type of sub shell as the highest energy sub shell
Critical elements
Elements that are heavily relied on for industry and society in areas such as renewable energy, electronics, food supply and medicine.
Effective nuclear charge
The effective nuclear charge of an atom is a measure of the attractive force felt by the valence shell electrons towards the nucleus
Effective nuclear charge + no. Protons - no. Total inner electrons
