Elements of Life Flashcards
What are atoms made up of?
Protons, Neutrons and Electrons
What are the charges for the Subatomic particles?
Proton = +1
Neutron= 0
Electron= -1
What is the relative mass for the subatomic particles?
Proton= 1
Neutron= 1
Electron= 1/2000
What is an ion and what does it mean when it has a negative or positive charge?
An ion is an atom with different numbers of protons and electrons. They either lose or gain electrons in order to have a full outer shell. Negative charge means there is one more electron than proton and positive have fewer electrons than protons.
What is an isotope?
Isotopes of an element are atoms with different number of neutrons, meaning the atomic number remains the same, but the mass number changes.
What decides the chemical properties of an element?
The number and arrangement of electrons.
What to the physical properties of an element often depend on?
The mass of the atom
How did John Dalton describe the structure of the atom and when?
He described them as being solid spheres at the start of he 19th century
How did J J Thomson describe the structure of the atom and when?
He describes them as being a positively charged sphere with negative electrons embedded in it (THE PLUM PUDDING MODEL!!) in 1897
How did Ernest Rutherford and his students Hans Geiger and Ernest Marsden prove the Plum Pudding Model incorrect and when?
By conducting the Geiger-Marsden experiment which involved firing alpha particles (positively charged) at an extremely thin sheet of gold in 1909
What were the results from the Geiger-Marsden experiment?
Most of the particles passed straight through the gold atoms and a very small amount were deflected (through more than 90 degrees)
What was the model that Rutherford came up with?
- There is a tiny, positively charged nucleus at the centre of he atoms where most of the mass is concentrated
- The nucleus is surrounded by a “cloud” of freely orbiting negative electrons
- Most of the atom is empty space
What did Henry Moseley discover and how did that effect how the nucleus was modelled?
He discovered the charge of the nucleus increased from one element to the other by units of 1, leading to Rutherford discovering that the nucleus contained positively charged particles called protons
What did James Chadwick discover?
He discovered the neutron
What were the 4 basic principles of Niels Bohr’s model?
- Electrons can only exist in fixed orbits (or shells)
- Each shell has a fixed energy
- When an electron moves between shells, electromagnetic ration is emitted or absorbed
- Because the energy of shells is fixed, the radiation will have a fixed frequency
How did the Bohr model also explain why some elements (the noble gases) are inert?
The shells of an atom can only hold a fixed number of electrons and that an elements reactivity is due to its electrons. When an atom has full shells, it is stable and doesn’t react.
What is the most accurate model we have today and what does it describe?
The most accurate model today involves quantum mechanics and basically shows that you never know where an electron is and which direction it’s going, but you can say how likely it is to be somewhere and electrons can act as waves as well as particles
What is relative mass?
The average mass of atoms of an element on a scale where an atom of carbon-12 is 12
Why do we uses relative mass?
Because the actual mass of an atom is very, very tiny and too small to weigh
What is relative isotopic mass?
The mass of an atom of an isotope of an element on a scale where an atom of carbon-12 is 12
How can you measure Relative Mass?
By using a mass spectrometer
What can a mass spectrometer be used to measure?
relative atomic mass, relative molecular mass, relative isotopic abundance and molecular structure
What are the 4 things that happen in a mass spectrometer?
- Vaporisation
- Ionisation
- Acceleration
- Detection
What occurs during the first step of mass spectrometry?
Vaporisation- the sample is turned into gas using an electrical heater.