The periodic Table Flashcards
Which elements are naturally occuring?
Up to and including uranium (92)
Where do the unnaturally occuring elements be created?
Synthesised by chemists in nucleur reactor or synchatron.
What are periods and groups? PG
In groups of elements with similar chemical and physical properties.
Periodis corresponds to the number of the outer shell of the atom.
How is the periodic table organised? 4 main principles
- Atomic number (not mass) determines order of elements.
- Repeating patterns of electron configuration observed when arranged in order of increasing energy level
- Arrangement of outer shell electrons is most important in determining chemical properties
- Periodic reccurance of similar properties results from periodic change in the electronic structure.
General patterns of metals ‘7
High melt b and m point Good conductors of heat and electricity Opaque Shiny appearence Ductile and malleable. Strong Form positive ions
General patterns of non metals ‘7
Low m and b point Poor conductors of heat and electricity Transparent in a thin sheet Dull brittle weak form negative ions
What are the trends in atomic radii?
Decreases across periodic table increases down group.
What element has the smallest radii and how big is it?
0.030nm
What is important to remember about radii?
DOUBLE FOR DIAMETER
Why is this trend? atomic radii
Going down a group, electrons are added to successive shells which are each further from the nucleus. Also the shells close to the nucleus create a shielding effect reducing the pull of the nucleus and the outer shell electrons.
Going across the group the elements have the same number of shells but protons and electrons are added, and so there is greater attraction between them, pulling the electrons in.
What is ionisation energy?
Energy required to remove an electron from an element in gaseous state (vacuum)
What is the unit for ionisation energy?
Kj mol^-1
Trends of ionisation energy?
Decreases going down a group
Increases as we move left to right across period
Why is this trend? Ionisation energy
The shells are further away from nucleus and shielding for groups
Shelding is constant and there are more protons and electrons are held closer.
what is electronegativity?
The measure of the degree to which an atom can attract an electron to itself.
Trends for electronegativity?
Going across a period it increases.
Going down a group electronegativity decreases.
Why is this trend? Electronegativity
Going across period, nuclear charge increases, and you get a higher electron attracting power.
Going down a group, there is shielding and the the shells are further from the nucleus
What is mettalic characteristics?
an elements ease of losing electrons
Trends? metallic characterisitics
Decreases across a periodic
increases down a group
Why is this trend? Metallic charastics
Across period, because there is higher nuclear charge and cant make positive ions
Down group, shells are further away from nucleus and shielding so easy to lose electrons
What is the oxidising strength of an element?
How readily an element gains electrons,
They are strong oxidisers because they oxidise something else and it itself becomes reduced.
What is the reducing strength of an element?
How readily an element loses electrons.
They are strong reductants and are themselves oxidises.
Why trends in oxidise and reducing?
going down a group elements give up electrons more easily due to shielding and distance from nucleus.
Going across period harder to give up electrons as nuclear charge increases.
