What is a period?
A period is a horizontal row of elements in the periodic table. Elements show trends in properties across a period.
What is a group?
A group is a vertical column in the periodic table. Elements in a group have similar chemical properties and their atoms have the same number of outer-shell electrons.
What are semi-metals or metalloids?Give some examples
These elements, such as silicon and germanium are semi-metals. Semi-metals or metalloids display properties between those of a metal and a non-metal.
What is periodicity?
Periodicity is a regular periodic variation of properties of elements with atomic number and position in the periodic table.
What is useful about periodicity?
Predictions can be made about likely properties of an element and it’s compounds.
Elements in the same vertical group have?
- the same number of electrons in the outer shell- the same type of orbitalsSo elements in the same group react in a similar way because they have a similar electron configuration.
What are the three factors that affect the atoms attraction to its outer- shell electrons?
- nuclear charge- distance from the nucleus- electron shielding
Why do the ionisation energies of elements across a period increase?
Across each period:- The number of protons increases, so there is more attraction acting on the the electrons.- Electrons are added to the same shell, so the outer shell is drawn inwards slightly. There is the same number of inter shells, so electron shielding will hardly change.- There is also a decrease in atomic radius across each period because the increased nuclear charge pulls the electrons in.
In ionisation energies, when starting the next period why is there a sharp decrease in ionisation energy between e end of one period and the start of the next?
The start of a new period reflects the addition of a new shell, further from the nucleus: - increased distance from the nucleus of the outermost shell.- increased electron shielding of the outermost shell by inner shells.
Why do the ionisation energies decrease down a group?
- The number of shells increases, so the distance of the outer electrons from the nucleus increases hence there is a weaker attraction to the nucleus.- There are more inner shells so the shielding effect on the outer electrons from the nuclear charge increases decreasing the nuclear attraction.- The number of protons also increases but the resulting increased attraction is far outweighed by the increase in electron distance and shielding.
What are the most striking trends across the periodic table?
- metals to non-metals- solid to gas.
Describe the trend in boiling points from group 1 to group 0
Groups 1 –> Group 4 : General increase in boiling points.Group 4 –> Group 5 : Sharp decrease in boiling point.Group 5 –> Group 0 : Comparatively low boiling points.
What is the distinct change in physical structure of elements from group 4 to 5?
- from giant structures to simple molecular structures- from strong forces to weak forces.
In periods 2 and 3 which elements have metallic bonds and which have covalent?
- All the metals form giant metallic structures- In group 2 and 3 , boron, silicon and carbon form giant covalent structures- everything else in group 2 and 3 form simple molecular structures.
The melting points of the metals Na, Mg and Al in period 3 increase across the period.Why?q
- The ionic charge increases and Na becomes 1+ while Al becomes 3+.- The ionic size decreases, increasing the strength of the metallic bonds.- These factors increase attraction.
