Chemistry assessment September 2016 Flashcards
Atoms are surrounded by what?
Electrons
What is each atom made up off?
A nucleus which contains protons and neutrons
What is the atomic number?
The number of protons in an atom
How are the elements arranged in the periodic table?
In ascending order of atomic number
The mass number of an atom is what?
Total of protons and neutrons
Atoms of the same element with different numbers of neutrons are called?
Isotopes of that element
Protons and electrons are what?
Oppositely charged
Do neutrons have a charge?
No, they have no charge
Nucleus of an atoms is always…
Positively charged
Why does an atom have a neutral overall charge?
It has the same number of electrons as protons
Protons and neutrons have what?
The same mass
What is the atomic number?
The number of protons in an atom
What is the mass number?
Total number of protons and neutrons in an atom
Where is the mass number shown on a chemical symbol?
At the top
Where is the atomic number shown on a chemical symbol?
At the bottom
What is the isotope of carbon?
-12 or 12C
How do you find out the neutron number on a chemical symbol?
Top number take away the bottom
What did John Dalton do?
He did experiments
Worked out some atomic weights
Invented symbols for atoms and molecules
Some of Dalton’s conclusions…
All matter is made from atoms
Atoms cannot be broken down into anything simpler.
Atoms are rearranged in a chemical reaction.
When was the electron discovered?
1897 by Jj Thompson
What did Jj show us?
That atoms contained smaller pieces
Ernest Rutherford showed us?
Experiments to show that an atom must contain a central nucleus
In an early model, the atom was imagined as what?
A sphere of positive charge with negatively charged electrons.
Radius of a typical atom?
10-10m
Mass- 10-23
The mass number of an atom is…
Never smaller than the atomic number.
It can be the same
The number of protons and neutrons in an atom is what?
The same
What charge do electrons have?
Negative charge
What happens if electrons are added or removed?
The atoms become charged and then is an ion
If a substance contains only one type of atom it is called an?
Element
What are isotopes?
Are atoms of an element with the normal number of protons and electrons but different numbers of neutrons
Isotopes have the same atomic number but
different mass number
The rate of reaction can be measured by what?
Rate at which a reactant is used up
Product is formed
Factors which affect the rate of reaction?
Temp Concentration Pressure of reacting gases Surface area Catalysts
Chemical reactions can only happen if?
Reactant particles collide with enough energy
Things to measure?
The mass of a substance (balance)
The volume of gas (gas syringe)
To increase the rate of reaction the concentration of a dissolved reactant is?
Increased
To increase the rate of reaction the pressure of reacting gas is?
Increased
To increase the rate of reaction solid reactants are?
Broken into smaller pieces
The minimum energy needed for particles to react is called the?
Activation energy
