1.2 The periodic table Flashcards
What was Newland’s law of octaves?
Every 8th element reacts similarly
Eg. If Li is 1st, then Na is 8th
What was the problem with Newland’s octaves
How did Doberainer arrange the elements?
In triads- elements with similar chemical properties go in groups of 3
Eg. Li, Na and K all react rapidly with water
Which 3 things did Mendeleev do when making the periodic table?
- He arranged them in order of atomic weight
- He left gaps for undiscovered elements when he thought one was missing
- When needed, he switched the order of some elements to fit the patterns of other elements in the same group
What is the problem with arranging elements in order of atomic weight?
The elements could appear in the wrong order due to the presence of isotopes.
Eg Te and I
What did Mendeleev do that was unusual?
He predicted the properties of undiscovered elements based off patterns from other elements in the same group
What is an element?
A substance made of only one type of atom
What is a compound?
A substance made of two or more elements chemically bonded together
What is a mixture?
Two or more substances not chemically bonded
What do periods in the periodic table show?
A new shell of electrons
eg. 2,8,1
= period 3
What do groups in the periodic table show?
How many electrons in the outer shell.
eg 2,8,1
= group 1
Define a diatomic molecule
Two atoms together
Describe the relationship between the size of halogens and the melting and boiling points
As the size of the atom increases, so does the boiling and melting point
Describe the trend in reactivity of halogens
The atoms get less reactive going down group 7
This is because the size of the atom decreases, causing the outer electron to become further from the positive attraction of the nucleus
The smaller atoms find it harder to gain an electron, making them less reactive
Why are the noble gases so reactive?
They already have full outer shells, since they’re group 0, so they don’t need to lose or gain any to become stable
