atomic structure and the periodic table Flashcards
revision
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 approximatley how many are there
they are listed in the periodic table. There are approximatley 100
elements can be classified in to two groups based on their properties. what are these called
metals and non-metals
elements may combine through chemical reaction to from new products. what are these new substances called
compounds
what is a compound
two or more elements combined chemically together in fixed proportions which can be represented by formulae
do compounds have the same properties as their constutuent elements
no they have diffrent properties
what is a mixture. does it have the same chemical properties as its constitient materials
a mixture consists of two or more elements or compounds not chemically combined together. it des have the same chemical properties
what are the methords through which mistures can be seperated (there are five)? do these involve chemical reactions
filteration. crysterlisation, simple distilation, fractional distilation and chromotography. they do nto invole chemical reactions
descrive and explain simple distilaion
simple distilation is used to seperate liquid from a soloution - the liquid boils off and condenses in the condenser. The thermometer will read the boiling point of the pure liquid. Contraty to evaporate, we get to keep the liquid.
describe and explain crystallisation/evaporation
evaporation is a tequnice for seperation of a solid dissolved in a solvent from a solvent (e.g salt from h2o)
The soloution is heated until all the solvent evapprates. the solids stay in the vessel.
crystalisation is similar but we only remove some of the solvant by evaporating to form a saturated soloution (the one where no more solids can be dissolved). Then we cool down the solution. As we do it, the solids start to crystalise, as it becomes less soluble at lower temprature. The crysatls can be collected and seperated from the solvant via filteration.
Describe and explain factional distilation
fractional distilation is a technique for seperation of a mixture of liquids. It works when liquids have diffrent boiling points.
The apparatus is similar to the one of simple distilation apparatus, with the additional fractional colounm placed on top of the heated flask.
The fractionating comloun contatin glass beads. It helps to serperate the compounds. In the indistry, mixtures are repeatedly condensed and vapourised. The column is hot at the bottom and cold at the top. The liquids will condencse at the diffrent heights of the column.
describe and explain filteraiton
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 chromatograhy
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 sperating 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/nuclear model and hot it came about
The nuclear model suggests that electrons orbit the nucleus at specific distances (shells) – it came about from the alpha scattering experiments
later experiments led to the discovery of smaller, positive prticles in the nucleus; what are these particles called?
protons
what did the work of James Chadwick provide evidence for
the existance 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 with there are electrons
state the relative masses and relative charges of the proton, nreutron and electron
masses: 1,1,very small ; charges: 1,0,-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 radious of a nucleous and what is ti compared to that of the atom
1 x 10^ -14 m and 1/10000
what name is given to the number of pretons in the nucleus
atomic number
atoms of the same element have the same number of which particle in the nucleous
protons