Chapter 7
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How did Mendeleev arrange elements?
1) in order of atomic mass 2) lining up elements in groups with similar properties
If the group properties did not fit, what did Mendeleev do with the elements?
Swapped them around and left gaps, assuming that the atomic mass measurements were incorrect and that some elements were yet to be discovered
What does the arrangement, pattern, and shape of the periodic table reveal?
trends among the elements
What are the positions of the elements in the periodic table linked to?
their physical and chemical properties
Why is the periodic table essential?
for predicting the properties of elements and their compounds
How are elements arranged?
in order of increasing atomic number
What is the same in each group of the periodic table?
Each element in a group has atoms with the same number of outer-shell electrons and similar properties
What does the number of the period give?
the number of the highest energy electron shell in an element’s atoms
What is periodicity?
A repeating trend in properties of the elements across each element
What is the most obvious periodicity in properties?
the trend from metals to non-metals
What properties of periodicity are there?
1) electron configuration 2) ionisation energy 3) structure 4) melting points
What is the chemistry of each element determined by?
its electron configuration, particularly the outer, highest energy electron shell
What does each period start with?
an electron in a new highest energy shell
What do the blocks in the periodic table correspond to?
their highest energy sub-shell
What are the 4 blocks in the periodic table?
2) s 2) p 3) f 4) d
What does ionisation energy measure?
how easily an atom loses electrons to form positive ions
What is the first ionisation energy?
The energy required to remove on electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
What are the factors involving ionisation energy?
1) atomic radius 2) nuclear charge 3) electron shielding
How are electrons held in their shells?
by attraction from the nucleus
Where will the first electron be lost from?
the highest energy level
How does atomic radius affect ionisation energy?
1) the greater the distance between the nucleus and outer electrons, the less the nuclear attraction 2) force of attraction decreases with increasing distance
How does nuclear charge affect ionisation energy?
The more protons in the nucleus, the greater the attraction between the nucleus and outer electrons
How does electron shielding affect ionisation energy?
inner-shell electrons repel outer-shell electron and reduces the attraction between nucleus and outer electrons
What is the shielding effect?
Electrons are negatively charged and so inner-shell electrons repel outer-shell electrons