topic 1 - key concepts in chemistry Flashcards
describe the history of the atom
dalton - atoms as solid spheres with different spheres making up different elements
jj thompson - plum pudding model
rutherford - nuclear model - result from gold foil experiments
bohr model - electrons and shells
what were the 3 key ideas of Daltons model?
- matter is made of atoms (tiny particles) which cannot be created, destroyed or divided.
- atoms of same element are identical
- different atoms combine to form new substances
where is the mass of an atom concentrated?
nucleus (positively charged)
what are the 3 subatomic particles?
protons, neutrons, electrons
what holds an atom together?
electrostatic force of attraction between positive nucleus and electrons
what is the charge of a proton?
+1
what is the relative mass of a proton?
1
what is the charge of a neutron?
0 (neutral)
what is the relative mass of a neutron?
1
what is the charge of an electron?
-1
what is the relative mass of an electron?
1/1840
how small is the nucleus’ radius?
10 000 x smaller than the atom
define mass number (atomic mass)
sum of protons and neutrons in nucleus of an atom
define the atomic number
number of protons in the nucleus of the atom
define an isotape
an atom with the same number of protons but different number of neutrons
what does the atomic number equal?
number of protons
how do you find the number of neutrons?
mass number - number of protons
how do you find the number of electrons?
atom = neutral + has the same number of protons and electrons
RAM calculation formula
(% of isotope a x mass of isotope a) + (% of isotope b x mass of isotope b) / 100
how did Mendeleev organise his periodic table?
by mass, and columns contained elements with similar properties
why did Mendeleev leave gaps in the periodic table?
for elements he believed to be undiscovered and keep elements with similar properties in the same vertical groups.
what were the problems with the mendeleevs table?
-isotapes were not known and he made no room for them
-discovery of the proton leading to atomic number was not discovered
how are elements arranged in the modern periodic table?
increasing atomic number
what are groups for?
vertical columns - show how many outer electrons each atom has
