unit 1 Flashcards
(20 cards)
what are the characteristics of the elements in the periodic table
- the atoms of the elements increase in mass as you go from left to right (starting with hydrigen) and downwards
- each element has an atomic number
- each element has a mass number
what are atomic numbers
it tells you how many protons the element contains. the atomic number increases by one with every element
what is a mass number
it tells you how many protons AND neutrons the element has in total
protons, electrons, neutrons charge
protons = positive
electrons = negative
neutrons = no charge
charge of an atom
an atom has no overall charge because the number of protons are the same as the number of electrons
how can you work out the number of neutrons
minus the mass number by the atomic number
who discovered the first model of the atom
J. J. Thompson and Ernest Rutherford
who discovered the new model of the atom that is used today
the Danish scientist Niels Bohr, in 1913
how are the electrons arranged
in electron shells around the nucleus
what are holding the electrons in place
electrostatic forces
the … shell has room for … electrons
first shell = 2 electrons
second and third shell = 8 electrons
trends going down group 1
group 1 is also called alkali metals:
the reactivity of elements increases as you go down because
- the atoms become larger
- the outer electron becomes further away from the nucleus
- the force of attraction between nucleus and outer electron decreases
- outer electron is lost more easily
(example) atomic structure of sodium (atomic number 11 mass number 23)
2, 8, 1
inert meaning
unreactive
all noble gases are…
inert/unreactive and do not form compounds
how are atoms arranged
the electrons are arranged in different electron shells/energy levels around the nucleus. the shell with the highest energy level is called the outermost electron shell (the outside shell).
why do elements react together
atoms are more stable when the outermost electron shell is completely full. groups 1 - 7 do not have full outer shells so they have to fill the outermost shell with electrons. 2 ways:
- atoms lose/gain electrons
- atoms share electrons
losing electrons (sodium ex)
a sodium atom has 1 electron on its outershell. to make the atom stable, it must lose the electron on the outershell, leaving it with a full new outershell.
- when an atom loses an electron it becomes an ion
- when a sodium ion forms, the symbol is Na+ because it has one less electron than the atom, therefore it has one more positvely charged proton than negatively charged electrons
gaining electrons (chlorine ex)
a chlorine atom has 7 electrons on its outershell, therefore it needs to gain one electron to make a full outershell and become stable.
- when it gains an electron, it becomes an ion.
- when a chlorine atom becomes an ion, the symbol changes from Cl to Cl-. this is because the atom now has one more negatively charged electron than positively charged protons
