Atomic Structure and the Periodic Table(1) Flashcards
What is an atom
An atom is the smallest part of an element that can exist
What is an element?
An element is a substance of only one type of atom.
How are the elements listed and approximately how many are there?
They are listed in the periodic table; there are approximately 100.
Elements can be classified into two groups based on their properties; what are these
groups?
Metals and non-metals
What is a compound?
Two or more elements combined chemically in fixed proportions which can be represented by formulae
Do compounds have the same properties as their constituent elements?
No, they have different properties.
What is a mixture? Does it have the same chemical properties as its
constituent materials?
A mixture consists of two or more elements not chemically combined together; it does have the same chemical properties
What are the methods through
which mixtures can be separated (there are 6)? Do these involve chemical reactions?
Filtration, crystallisation, simple distillation, fractional distillation and chromatography; they do not involve chemical reactions
Describe and explain simple distillation in steps
Step 1
Step1
Simple distillation is used to separate liquid from a solution – the liquid boils off and condenses in the condenser.
Describe and explain simple distillation.
Step 2
Step 2
The thermometer will read the boiling point of the pure liquid.
Describe the difference between simple distillation and evaparation
Simple distillation keeps the liquids where as evaporation doesn’t
Describe and explain evaporation
Evaporation is a technique for separation of a solid dissolved in a solvent from a solvent (e.g. salt from H(small2)O)
The solution is heated until all the solvent evaporates; the solids stays in the vessel.
Describe and explain Crystallisation
Crystallisation is similar to evaparation ,
but we only remove some of the solvent by evaporation to form a saturated solution (the one where no more solid can be dissolved). Then, we cool down the solution.
As we do it, the solid starts to crystallise, as it becomes less soluble at lower temperatures.
The crystals can be collected and separated from the solvent via filtration.
What is a solvent
A solvent is the term used for the liquid in which a substance (solute) is dissolved
What is a solute
A solute is a solid, liquid, or gas which is dissolved to make a solution
What is a solution
A solution is a homogeneous(similar) of one or more solutes dissolved in a solvent
Describe and explain fractional distillation
Fractional distillation is a technique for separation of a mixture of liquids. It works when liquids have different boiling points.
What makes the apparatus of a simple distillation different to a fractional distillation
It has an addittional fractionating column placed on top of the heated flask
What does the fractionating column contain and whats its purpose
It contains glass beads which help to separate the compounds
What happens in industry in fractional distillation
mixtures are repeatedly condensed and vapourised. The column is hot at the bottom and cold at the top. The liquids will condense at different heights of the column
Describe and explain filtration
3 steps
Filtration is used to separate an insoluble solid suspended in a liquid.
The insoluble solid (called a residue) gets caught in the filter paper, because the particles are too big to fit through the holes in the paper.
The filtrate is the substance that comes through the filter paper.
What is the apparatus used in filtration
filter paper + funnel.
Describe and explain chromatography
Chromatography is used to separate a mixture of substances dissolved in a solvent.
Explain paper Chromatography in steps
Step 1
Step1
place a piece of paper with a spot containing a mixture in a beaker with some solvent
Explain paper Chromatography in steps
Step 2
Step 2
The bottom of the paper has to be in contact with the solvent.
Explain paper Chromatography in steps
Step 3
The solvent level will slowly start to rise, thus separating the spot (mixture) into few spots (components).
What is a separating funnel?
A separatory funnel is an apparatus for separating immiscible ( can’t mix) liquids.
What is a immiscible liquid
Immiscible liquids are those which won’t mix to give a single phase
Eg oil and water
What will two immiscible liquids of different densities form in a funnel
Two distinct layers in the separatory funnel
In a separating funnel what can you do to the bottom layer (the liquid with a greater density)
You can run off the bottom layer to a separate vessel
.
.
Describe the plum-pudding model
The atom is a ball of positive charge with negative electron embedded in it.
Describe the Bohr/nuclear model
The nuclear model suggests that electrons orbit the nucleus at specific distances (shells)
How did the bohr/nuclear model come about
it came about from the alpha scattering experiments
Later experiments led to the discovery of smaller, positive
particles in the nucleus; what are these particles called?
Protons
What did the work of James Chadwick provide evidence
for?
The existence of neutrons in the nucleus
Describe the structure of an atom
The atom has a small central nucleus (made up of protons and neutrons) around which there are electrons
State the relative masses and relative charges of the proton,
neutron and electron
Proton Mass 1 Charge +1
Neutron Mass 1 Charge 0
Electron Mass 1/2000 Charge -1
Explain why atoms are electrically neutral.
They have the same number of electrons and protons
What is the radius of an atom?
0.1 nm
What is the radius of an atom?
0.1 nm
What is the radius of a nucleus and what is it compared to that of the atom?
the radius of an atom is about 0.1 nm (1 × 10-10 m)
the radius of a nucleus (1 × 10-14 m) is less than 110 , 000 of the radius of an atom
What name is given to the number of protons in the
nucleus?
Atomic number
Atoms of the same element have the same number of which particle
in the nucleus?
Protons
Where is the majority of mass of an atom?
The nucleus