Atomic Structure And The Periodic Table Flashcards
What is an atom?
the smallest particle of an element that can exist
What is an element?
a substance that contains 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 are compounds?
Materials made of the atoms of two or more different elements, which have chemically combined.
Do compounds have the same properties as their constituent elements?
No, they have different properties
What is a mixture?
material composed of two or more elements or compounds that are physically mixed together but not chemically combined (it does have the same chemical properties)
What are the methods through which mixture can be separated?
Filtration, crystallisation, simple distillation, fractional distillation and chromatography (they don’t 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
- crystallisation is similar to evaporation
- 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 in 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
column.
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 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 plum pudding model suggested that an atom is a ball of positive charge with negative electrons in embedded in it
Describe the Bohr model
-single electron circled around nucleus in orbits
-each orbit had a specific energy
-orbits closer to nucleus = lower energy
-lots of empty space between nucleus and electron
(It came about from the alpha scattering experiments)
What is a proton?
positively charged particle found in the nucleus
What is a neutron?
a particle that has no charge and that is inside the nucleus
What is an electron?
a negatively charged subatomic particle
What did 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 charges of the subatomic particles
Protons: +1, neutrons: 0, electrons: -1
State the relative masses of subatomic particles
Protons: 1, neutrons: 1, electrons: 1/1835
Explain why atoms are electrically neutral.
They have the same number of electrons and protons
What is the radius of an atom?
0.1 nanometers
What is the radius of a nucleus and what is it compared to that of the atom?
1 x 10-14 m and 1/10000
What is the atomic number?
the number of protons in an atom
Where is the majority of mass of an atom?
nucleus
What is the mass number?
the total number of protons and neutrons in a nucleus.
How does one calculate the number of neutrons using mass number and atomic number?
mass number - atomic number
What is an isotope?
Atoms of the same element that have different numbers of neutrons but the same number of protons
Do isotopes of a certain element have the same chemical properties?
they have the same chemical properties as they have the same electronic structure
What is relative atomic mass?
An average mass of isotopes making up an element and how much of each element there is.
What are ions?
Ions are charged particles. They are formed when atoms lose electrons (positive ions) or gain (negative ions) electrons.
E.g. sodium positive ion, Na+ , has an electronic configuration of 2,8 (same as Ne). An atom of sodium has lost one electron.
Compare the properties of metals and non-metals
Metals: High boiling and melting point, conduct heat and electricity, shiny, malleable, high density, basic oxides.
Non metals: low boiling and melting point, don’t conduct heat and electricity except graphite, dull, brittle, low density, acidic oxides.
What is formed when a metal reacts with a non-metal?
An ionic compound (made of positive and negative ions).
What is formed when a non-metal reacts with a non-metal?
A molecular compound containing covalently bonded atoms.
Atoms share electrons, as opposed to transferring electrons between each other (cf. ionic compounds).
What is a solute?
the substance that is dissolved
What is a solvent?
the substance in which the solute dissolves
What is a solution?
a mixture of solute and solvent
What is miscible?
two liquids that are soluble in each other