Topic 1 - key concepts Flashcards
What are the three ideas in John Dalton’s theory about the atom?
Atoms cannot be created, divided or destroyed
Atoms of the same element are exactly the same and atoms of different elements are different
Atoms join with other atoms to make new substances
What discovery caused the oriGina dalton model of an atom to change?
The discovery of subatomic particles
How did JJ Thomson discover the electron?
Tho pain experimented with a cathode ray tube
The beam moved towards the positively charged plate so we knew that the particles must have a negative charge
Describe the atomic model proposed by JJ Thomson
Plum pudding model
Negatively charged electrons scattered through a positively charged material
What did Ernest Rutherford discover from his gold foil experiment?
He shot a beam of positively charged particles at sheet of gold foil
Most particles passed straight through suggesting that atoms were mostly empty space
A few particles were deflected and a few bounced directly back showing that there must be a tiny dense and positively charged nucleus
Describe rutherfors’s new model of the atom
Mass is concentrated in central nucleus
Mostly empty space
Electrons travel in random paths around the nucleus
Describe the structure of an atom
Small central nucleus made up of protons and neutrons
Electrons orbit the nucleus in shells
What is the radius of a nucleus?
1x 10^-14m
How large is a nucleus compared to the radius of an atom?
1/10000 of the atomic radius
What are the relative masses of protons, neutrons and electrons?
Proton: 1
Neutron: 1
Electron: 1/1850
What are the relative charges of protons, neutrons and electrons?
Proton: +1
Neutron:0
Electron:-1
Why do atoms contain equal numbers of protons and electrons?
Atoms are stable with no overall charge
Protons are positively charged and electrons are negatively so they must have the same number to balance the charge out
Where is the mass of an atom concentrated?
In the nucleus
What does the atomic number of an atom represent?
The number of protons
What does the mass number of an atom mean?
It is the number of protons and neutrons in the atom
What is an isotope?
Atoms of the same element that have a different number of neutrons
Why is the relative atomic mass not always a whole number?
Different isotopes have different mass numbers the the ram is an average
What two values would be required to calculate the relative atomic mass of chlorine?
The mass number and relative abundance’s of all the isotopes of chlorine
How did Mendeleev arrange the elements in his periodic table?
Elements were arranged with increasing atomic masses
The ones with similar properties were put into groups
He switched the position of some elements
He left gaps for undiscovered elements
How was Mendeleev able to predict the properties of new elements?
He left gaps in his periodic table
He used the properties of elements next to these gaps to predict the properties of undiscovered elements
Mendeleev’s table lacked some amount of accuracy in the way he’d ordered his elements, why?
Isotopes were poorly understood at the time
Protons and neutrons and not yet been discovered
How are elements arranged in the modern periodic table?
In order of increasing atomic number
What do elements in the same group have?
Similar chemical properties
Why do elements in the same column have similar chemical properties?
Same number of outer shell electrons
The number of outer shell electrons determines how an atom reacts
What does the period number tell you about all the elements in that period?
Elements in the same period have the same number of electron shells
What does the group number tell you about all the elements in that group?
They will have the same number of outer electrons
On which side of the periodic table are the metals positioned?
On the left
Hat determines whether an element is a metal or non-metal?
The atomic structures of the elements
What is the maximum number of electrons allowed in each of the first three shells?
1: 2
2: 8
3: 8
When are atoms most stable?
When they have full electrons shells
What is an ionic bond?
A bond between a metal and non-metal involving the transfer of electrons
In terms of electrons, describe what happens to the metal and non-metal when an ionic bond forms
The metal atom loses electrons to become a positively charged ion
The non-metal gains electrons to become a negatively charged ion
What is an ion?
An atom or group of atoms with a positive or negative charge
If an ion is positively charged, has it lost or gained electrons?
It has lost them