ST.1 Trends in the Periodic Table H (CCS) Flashcards
(18 cards)
What is a row in the periodic table called?
A period
What is a column in the periodic table called?
A group
How are elements grouped?
Elements of the same group of the Periodic Table have similar chemical properties
What is the size of an atom indicated by?
By its covalent radius
What is the covalent radius of an element?
The covalent radius of an element is half the distance between the nuclei of 2 of its bonded atoms
What happens to the covalent radius as you go across a period?
In general, the radius decreases across a period
What happens to the covalent radius as you go down a group?
In general, the radius increases down a group
Why is there no data for noble gases on page 7
Noble gases don’t form bonds
What does increased nuclear charge mean?
Increased nuclear charge means the nuclear attraction for electrons is stronger so the electrons are held more tightly
What is periodicity?
Periodicity is the patterns that recur at regular intervals
How are elements grouped?
Elements in the periodic table are grouped in a way that they are organised into their properties
What order are elements grouped in?
Elements are grouped in order of atomic number
Explain why sodium is larger than phosphorus
- Na is larger than K as Na has a larger covalent radius than phosphorus (160pm v 109pm) because Na has 11 protons where as K has 15.
- The stronger nuclear charge in K holds the electrons more tightly to the nucleus
- Therefore the covalent radius is smaller in K
Explain why sodium is smaller than rubidium
- Rubidium is larger than sodium (215pm vs 160pm) because Rb has 2 more complete electron shells than Na
- So the outer electrons in Rb are more shielded from the nuclear charge and held less tightly
- Therefore the covalent radius in Rb is larger
Explain why the potassium ion is smaller than the potassium atom
A potassium atom has electrons in four shells but the ion only has electrons in three shells. There is less shielding so they’re held more tightly and the ion is smaller
What happens across a period?
Across a period, the covalent radius decreases as the number of protons increases. This increased the nuclear attraction for the electrons, electrons are held more tightly, thus decreasing the size of the atoms
What happens down a group?
Down a group, the covalent radius increases as there are more energy levels, resulting in an increased shielding effect. This reduces the strength of the nuclear attraction for electrons, electrons are not held as tightly, thus increasing the size of the atoms
What is ionisation energy?
The first ionisation energy of an element is the energy required to remove one mole of electrons from one mole of atoms in the gaseous state
