SAC 1 - Elements, Periodic Table and Quantifying Atoms & Compounds Flashcards
Matter
Any substance that has mass and takes up space by having volume
What is matter made up of?
Atom
Atom
smallest part of an element capable of existence
If an atom is divided
ceases to be an atom of the original element
Atoms can be broken down into
subatomic particles
Subatomic particles
protons, neutrons and electrons
Element
Pure substance containing only a single type of atom
Where is the nucleus in an atom?
In the centre
Most of the atom is
empty space
What does a nucleus contain?
Nucleons, which account for most of the mass. Protons and Neutrons
Protons
Positively charged particle inside the nucleus of an atom.
Neutrons
Neutral particle inside the nucleus of an atom
Electrons
- negative charged particles
- orbit the nucleus in electron shells
- much smaller than protons and neutrons
Valence Electrons
Electrons in the outermost shell
Atomic number
The number of protons in the nucleus of an atom
Number of protons =
Number of electrons (hence neutral)
All atoms of the same element
Contain the same number of protons
Periodic Table
Table of chemical elements in which elements are arranged in order of increasing atomic number
Mass Number
Mass of an atom, the total number of protons and neutrons in the nucleus of an atom, no units as it is relevant to Carbon 12
Isotope
Atoms of the same element with different numbers of neutrons, but same number of protons. Have the same atomic number but different mass numbers.
Nucleotide notation
Mass number on top left.
Elements in the same group
Have similar reactivity and properties
Most reactive groups
Alkali earth metals, and halogens
Electron Arrangement is responsible for
chemistry and properties of an element
Electron configurations
The way in which electrons are arranged around the nucleus of an atom
Stable atom electron arrangement
Electrons are as close to the nucleus as possible (ground state)
Excited state
when electrons jump to higher energy levels
Bohr Model rules
- Each electron shell (or energy level) holds a different number of electrons
- Electrons will fill shells closest to the nucleus first
- Electrons fill and empty shells in a particular order
Bohr Model Formula
The maximum number of electrons in each shell is 2n^2 where n is the shell number
Which shell has the lowest energy?
Shell 1
Electrons that are in the same shell
Are the same distance from the nucleus and have the same energy
Emission Spectra
element is heated and atom gains energy, atoms go into excited state. When electrons drop back, emits light at a frequency
Schrodinger model
subshell model
subshells
energy levels of very similar energy within each shell
Orbitals
Regions of space in which the electrons move within a subshell.
Pauli Exclusion principle
Each orbital holds a maximum of two electrons
Properties
Each element has a set of physical and chemical properties that distinguishes it from other elements.
Properties used to identify an element
Melting and boiling points, reactivity with other substances.
Horizontal Rows of Periodic table
Periods. The number of occupied electron shells.
Vertical Columns of the periodic table
Groups. Same number of valence electrons.
Blocks F and g
Lanthanides and Actinides.
What is an Ion?
An ion is a charged particle that has either lost or gained valence electrons to become stable.
Cations
Ions that have lost electrons
Anions
Ions that have gained electrons
Monoatomic ion
Ions containing one atom only
Polyatomic Ion
Ions made up of more than one atom
Electrostatic attraction
attraction between the negative valence electrons and positive nucleus. Used to explain trends in an element.
Atomic Radius
radius of an atom (measured in pictometers)
Ionisation energy
Energy required to remove an electron froma gaseous atom
First Ionisation energy
energy required to remove one electron
The more ionisation energy required
the stronger the attraction between the nucleus and the valence electrons
Electronegativity
a measure of an atom’s ability to attract electrons. The bigger the number, the better the attraction
Metallic character
Ease with which elements loose valence electrons
Non-metallic character
Ease with which elements gain valence electrons
Core charge formula
number of protons - number of inner shell electrons
Core charge
nuclear pull on the outer-shell electrons
The greater the core charge
The greater the nuclear pull
As you move down a group
- atomic radius increases
- first ionisation energy decreases
- electronegativity decreases
- metallic character increases
- non - metallic character decreases
Electronegativity is determine by
core charge and distance of valence shell from nucleus
As you move across a period
Atomic radius decreases
First ionisation energy increase
Electronegativity increases
Metallic character decreases
Non-metallic character increases
Reactivity
describes how easy it is for an atom of an element to gain or loose electrons
Reactivity depends on
The number of electron shells present
The number of valence electrons in the outer shell
The size of the atomic radius
The core charge of the atom
Increase in atomic radius
Reactivity
Increases for elements that tend to lose electrons (metals)
Decreases for elements that tend to gain electrons (non-metals
Increase in core charge
Reactivity
Decreases for elements that tend to lose electrons (metals)
Increases for elements that tend to gain electrons (non-metals)
Increase in electronegativity
Reactivity
Decreases for elements that tend to lose electrons (metals)
Increases for elements that tend to gain electrons (non-metals)
Critical features
Elements that are vital and considered in limited supply unless they are recycled
sources could become depleted in 50–100 years
Endangered Element
Elements that have a limited supply left on Earth
Critical Elements
Help - helium
Protect - phosphorus
P - post transition elements
R - rare earth metals
And
M - metalloids
Recycle
Convert into useful material
Every measurement has
A level of uncertainty
Significant figures
indicate the level of precision in a measurement
Number of Significant features allowed in an answer
Same as the least precise value
Rules for significant figures
Leading zeros never count, trailing zeros always count
Relative Scale of Atomic Mass
When measuring the mass of an atom, relevant measurements are used.
Why is Carbon - 12 used
due to its stability and abundance
Relative Isotopic Mass
Mass of the individual isotopes
Relative Atomic Mass
The weighted average of the relative masses of the isotopes (no units)
Relative Molecular Mass
Same as Molar Mass but has no units. Sum of relative atomic masses of molecules
Relative Formula Mass
Sum of relative atomic mass
Avagadros Constant
6.02 x 10^26
1 mole
6.02 x 10^23
Units for molar mass
grams/mol