principles of chemistry - the periodic table Flashcards
how is the periodic table organised?
- columns are called groups. they indicate the number of electrons in the outer shell of an atom.
- rows are called periods. they indicate the number of shells (energy levels) in an atom
how to deduce electronic configurations
example – chlorine (Cl)
- use the periodic table to look up the atomic number. Chlorine’s atomic number (number of protons) is 17.
- remember the number of protons = number of electrons. Therefore chlorine has 17 electrons.
- Arrange the electrons in levels (shells):
1st shell can hold a maximum of 2
2nd can hold a maximum of 8
3rd can also hold 8
Therefore the electron arrangement for chlorine (17 electrons in total) will be written as 2,8,7
4) Check to make sure that the electrons add up to the right number
this can then be drawn
how do you use electrical conductivity and the acid-base character of oxides to classify elements as metals or non-metals?
Metals
- conduct electricity
- have oxides which are basic, reacting with acids to give a salt and water
Non – Metals
- do not conduct electricity (except for graphite)
- have oxides which are acidic or neutral
how to identify an element as a metal or a non-metal according to its position in the Periodic Table
- metals on the left of the Periodic Table.
- non - metals on the top-right, plus Hydrogen.
how are the electronic configuration of a main group element related to its position in the Periodic Table?
- elements in the same group have the same number of electrons in their outer shell.
- this is why elements from the same group have similar properties.
why do elements in the same group of the Periodic Table have similar chemical properties?
elements in the same group of the periodic table have the same number of electrons in their outer shells, which means they have similar chemical properties.
why do the noble gases (Group 0) do not readily react?
the noble gases are inert (unreactive) because they have a full outer shell of electrons
