Chemistry-Module 3 Flashcards
How are the elements in the modern periodic table arranged?
the elements are arranged in order of increasing atomic number
How is the periodic table organised?
it’s organised into periods(rows), groups(columbs) and blocks
What is the trend of elements in a period?
the elements have the same number of electron shells and as a result have repeating trends in physical and chemical properties(periodicity)
What is the trend of elements in a group?
The same number of electrons in their outer shell and as a result have have similar physical and chemical properties
Define first ionisation energy
The energy needed to remove 1 mole of electrons from 1 mole of gaseous atoms
Explain the trend in ionisation energy across period 2
The ionisation energy increases
How has the the periodic law been developed?
Elements were first arranged by their physical and chemical properties and by their relative atomic mass
Then they were arranged by proton number in the modern periodic table
What is the periodic law?
It states that if you arrange elements in order of increasing atomic number then their chemical and physical properties will repeat in a systematic way that can be predicted
Why was the periodic table extended through discovery and confirmation of new elements?
Mendeleev arranged the elements in order of atomic mass and left spaces where the next element didn’t fit so he could keep elements with similar chemical properties
Explain the trend in first ionisation energies down a group
As you go down a group the first ionisation energy decreases and it gets easier to remove outer electrons because:
. the number of electrons increases which means that the atomic radius gets larger
. There are more inner electron shells shielding the outer electron from the nucleus
. Therefore, the attraction between the nucleus and the outer electrons is reduced
What are the factors affecting ionisation energy?
.Nuclear charge- the more protons in the nucleus, the more positively charged the nucleus is and the stronger the attraction for the electrons
.Atomic radius- the less electrons, the closer the outer electron to the nucleus so the stronger the attraction between the nucleus and outer electrons
.Shielding- the more electrons between the outer electrons and nucleus, the less the attraction toward the nuclear charge
Why is there a drop in ionisation energy between groups?
It’s due to electron repulsion
Define successive ionisation energy
Second ionisation energy etc….
Define second ionisation energy
The energy needed to remove 1 electron from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions
Why does successive ionisation energy increase within each shell?
The electrons are being removed from an increasingly positive ion
There’s less electron repulsion amongst the remaining electrons so more energy is needed to remove the next electron
