Unit 1: Atomic Structure Flashcards
(46 cards)
Define Element
A pure chemical substance composed of atoms with the same number of protons in the atomic nucleus. Cannot be broken down into a simpler substance.
Define an atom
The smallest particle of an element to show characteristic properties of that element.
Define a compound.
Compounds consist of atoms of different elements chemically bonded together into a fixed ratio.
The chemical properties of a compound are different from that of its constituent elements.
Define a mixture.
Mixtures contain more that one element or compound in no fixed ratio.
- Components of a mixture can be separated by physical methods
What is a homogenous mixture?
- A homogenous mixture has a uniform composition and properties throughout.
- To form a homogenous mixture the inter-particle attraction within the different components must be similar to the components within the mixture
What is a heterogenous mixture?
- A heterogenous mixture has a non-uniform composition, and its properties are not the same thro.
-The interactions between the components are different in nature
Explain the methods of separating the components of a mixture.
- Filtration
Solid is separated from a liquid or a gas through a membrane. - Distillation
Used to separate a solvent and a solute. The solvent has a lower boiling point then the solute and is collected as a gas. which then passes through a condensing tube and collected into a beaker. - Paper chromatography.
Small spots of solutions containing the samples are placed on a baseline on a paper suspended. The paper is the dipped in water and the solutions have different affinities for water so they travel different distances along the paper.
State the kinetic molecular theory
Matter exists in different states as determines by the temperature and the pressure, Solid, Liquid and Gas
What is temperature in chemistry terms?
The measure of the average kinetic energy of the particles of the substance.
What is diffusion?
The process by which the particles of a substance spread out more evenly as a result of their random movement.
Define sublimation
Solid to a gas without going through the liquid state
Define deposition.
When a gas turns directly into a solid
When does boiling happen
At a fixed temperature for a given pressure. When the vapour pressure is equal to the external pressure
- As liquid heats more particle enter the vapour state and add to the vapour pressure.
When does Evaporation occur?
Only at the surface of the substance and takes place over a range of temperatures.
When is temperature constant?
During changes of state
What did John Dalton propose in the 19th century?
- All matter is composed of tiny invisible particles called atoms
- Atoms cannot be created or destroyed
- Atoms of the same element are alike in every way
- Atoms
How did Ernest Rutherford discover there was a positively charged nucleus in the middle of the atom?
By firing positively charged alpha particles at a piece of gold foil the particles mostly passed through but only a few were repelled when they hit a small dense positvley charged nucleus
How did JJ Thompson discover the atom had electrons?
When a high voltage is applied across two electrodes to different metals a stream of negatively charged particles is produced.
What happens when positrons and electrons (anti-particles) collide?
They destroy each other and release energy in the form of high energy photons called gamma rays.
What is the number of protons in an element given by?
The atomic number
How do you derive the number of neutrons in an element.
mass number - atomic number
Define isotope.
Atoms of the same element with a different number of neutrons
Do isotopes show the same chemical properties?
Yes, the difference in number of neutrons makes no difference in how they react as they still occupy the same place on the periodic table.
What happens when a nucleus has too many or few neutrons.
It gives off radiation to become radioactive and changing to a more stable nucleus.
