4.1.1 A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes Flashcards
What are the three different isotopes of hydrogen
- Tritium
- Deuterium
- Protium
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.
Elements can be classified into two groups based on their properties; what are these groups?
Metals and non-metals
Elements may combine through chemical reactions to form new products; what are these new substances called?
Compounds
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 or compounds not chemically combined together; it does have the same chemical properties
What are the methods through
which mixtures can be separated (there are five)? Do these involve chemical reactions?
Filtration, crystallisation, simple distillation, fractional distillation and chromatography; they do not involve chemical reactions
Describe and explain simple distillation.
Simple distillation is used to separate liquid from a solution – the liquid boils off and condenses in the condenser. The thermometer will read the
boiling point of the pure liquid. Contrary to evaporation, we get to keep the liquid.
Describe and explain crystallisation/evaporation.
Evaporation is a technique for separation of a solid dissolved in a solvent
The solution is heated until all the solvent evaporates; the solids stays in the vessel.
Crystallisation is similar, 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.
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.
The apparatus is similar to the one of simple distillation apparatus, with the additional fractionating column placed on top of the heated flask.
The fractionating column contains glass beads. It helps to separate the compounds. In industry, 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
Describe and explain filtration
Filtration is used to separate an insoluble solid is 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. Apparatus: filter paper + funnel.
Describe and explain chromatography
Chromatography is used to separate a mixture of substances dissolved in a solvent.
In paper chromatography, we place a piece of paper with a spot containing a mixture in a beaker with some solvent. The bottom of the paper has to be in contact with
the solvent. 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 liquids. Two immiscible liquids of different densities will form two distinct layers in
the separatory funnel.
We can run off the bottom layer (the liquid with greater density) 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 model
The Bohr model suggests that electrons orbit the nucleus at specific distances (shells)
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
Masses: 1, 1, very small ;
Charges: 1, 0 , -1 (respectively)
Explain why atoms are electrically neutral.
They have the same number of electrons and protons which cancel eachother out
What is the radius of an atom?
0.1nm
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 nucelus
What is the mass number?
The total number of protons and neutrons
What is an isotope? Do isotopes of a certain element have the same chemical properties?
Atoms of the same element (same proton number) that have a different number of neutrons.
They have the same chemical properties as they have the same electronic structure
What is the relative atomic mass?
The relative atomic mass of an element is an average value that takes account of the abundance of the isotopes of the element
