module 3 - the periodic table Flashcards
giving Mendeleev the credit he deserves (79 cards)
How did Mendeleev arrange the elements across a period?
In order of atomic mass!
How did Mendeleev arrange the elements in groups?
He put the elements in groups with similar properties
what does the number of the period tell you?
the highest energy shell number, in an element’s atoms
What is periodicity??
A repeating trend in properties of elements across each period
How is the modern periodic table arranged?
In order of increasing atomic number
What is the chemistry of each element determined by?
Its electron configuration
What does each period start with?
An electron in a new highest energy shell
What are the 5 properties that show periodicity across the periods?
- electron configuration
- metal to non-metal
- ionisation energies
- structure
- melting point
What is the trend in electron configuration for each period?
The s and p sub-shells are filled in the same way
What is the trend in electron configuration in each group?
Elements in each group have atoms with the same number of electrons in each sub-shell
What des the similarity in each group give to those elements in that group?
Similar chemistry/ chemical reactions
What name is given to group 1 elements?
Alkali metals
What name is given to group 2 elements?
Alkaline earth metals
Which group did Mendeleev miss out in the periodic table? why was he unaware of it?
Group 18 (noble gases). They’re very unreactive and no elements from that group had been discovered at the time.
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 1 electron from each atom in 1 mole of gaseous atoms of an element to form 1 mole of gaseous 1+ ions
Write the equation for the 1st ionisation energy of sodium.
Na (g) —> Na+ (g) + e -
what energy level is the first electron lost from? What’s its attraction to the nucleus like?
- highest energy level
- experiences the least attraction from the nucleus
what 3 factors affect the attraction between the nucleus and the outer electrons of an atom (and the ionisation energy)?
- atomic radius
- nuclear charge
- electron shielding
how does atomic radius affect nuclear attraction with the outermost electrons?
- greater distance between nucleus and outer electrons = less nuclear attraction
- atomic radius has a large effect
how does nuclear charge affect nuclear attraction with the outer electrons?
more protons in nucleus = greater attraction between nucleus and outer electrons
how does electron shielding affect nuclear attraction with the outer electrons?
- inner shell electrons repel outer shell electrons = shielding effect
- reduces attraction between nucleus and outer electrons
In helium, why is the 2nd ionisation energy greater?
- after the 1st electron is lost, the last electron is pulled closer to the nucleus
- the nuclear attraction on the remaining electron increases and more ionisation energy is needed to remove it
define the second ionisation energy?
the energy required to remove 1 electron from each atom in 1 mole of gaseous 1+ ions of an element to form 1 mole of gaseous 2+ ions