Please enable JavaScript.
Coggle requires JavaScript to display documents.
science semester 2 2019 (29/7/19 (an atom is made up of multiple parts: (a…
science semester 2 2019
29/7/19
an atom is the smallest part of an element that still retains the properties of that element. it is the smallest particle of matter and means 'indivisible' or unable to be broken down.
-
around the nucleus moving at very high speeds are one or more electrons. electrons can be found i a space called the electron cloud. electrons are 2-thousandth of the mass of protons or neutrons. electrons have a negative charge equal in size to charge of a portion.
the atomic number of an atom is the number of protons in the nucleus of that atom. the atomic number is represented by the symbol 'Z'. the mass number is the number of protons plus the number of neutrons in an atom. it is represented by the symbol 'A'.
elements are pure substances made up of only one type of atom. they cannot be broken down as they are already in their simplest form.
today we officially recognize more than 118 different elements, which have been discovered over time.
some of these occur naturally, while others are made or synthesized.
elements can be further classified into 3 groups- metals, non-metals and metalloids (semi metals).
elements are identified through the use of CHEMICAL SYMBOLS. these symbols are originated from the need for a universal language across countries. there is a chemical symbol for each element that is the same worldwide.
chemical symbols for elements are made using the letters of the alphabet. some elements have one letter and others have 2 to avoid confusion.
the first letter of a chemical symbol is always a CAPITAL letter and the second letter is always LOWERCASE e.g. Cu, H, Be.
-
a CHEMICAL FORMULA is used when there is more then one atom in a particle of a substance e.g. oxygen gas io Oz.
-
1/8/19
atoms in elements
elements are made up of atoms but only have one type of them. these atoms can be arranged in different ways;
-
-
-
monatomic elements
these are made up of one atom (individual atoms). these are rare and thereare only 6 of the 98 naturally occurring elements that are monatomic (Ne, Ar, Kr, Xe, Rn). helium in monatomic and lighter than air so it floats.
neon is used in neon lights.
argon used to be used in old light globes to stop the filament from burning
molecular elements
molecules are clusters of 2 or more atoms bonded together. most non-metallic elements are made up of molecules.gases are written with the molecular formula of how many atoms are joined together. oxygen os O2, nitrogen is N2, hydrogen is H2, chlorine is Cl2.
crystal lattices
-
metallic
80% of elements are metals. these are dense (hard) and strong and exist as solids at room temperature. these lattices can slide and move over each other to become wires and sheets. they are also good conductors of heat and electricity.
-
5/8/19
compounds
are substances that are made u of more than 1 atom. they have a specific set of characteristics or properties.
-
mixtures
a mixture is made up of more than 1 substance, where the substances are chemically bonded together. this means that the substances are chemically bonded together. this means that the substances can be easily separated.
example is water-salt can be evaporated from the water.
there are many different types of mixtures that we use everyday. one common type of mixture is a solution. the dissolving solid is known as the solute. the liquid in which the solute dissolves is known as the solvent.
7/8/19
alloys
an alloy is a mixture of a metal with other metals or non-metals. alloys often have different properties than pure metals, such as increased strength, hardness or resistance to corrosion.
examples:
- steel is an alloy of iron (Fe) and carbon (C). the addition of carbon makes the metal harder and less prone to rusting,
- brass-alloy of copper and zinc.
-silver coins-alloy of copper and nickel.
-gold coins-alloy of copper, aluminium and nickel.
minerals
a mineral is a naturally occurring chemical substance that is solid and inorganic (has not been made by an animal, plant, or other organism). atoms within a mineral are arranged in orderly way in a crystal lattice. rocks are made up of minerals. many minerals can dissolve in water. some are also found in groundwater, lakes and oceans. some elements can be found as pure element but most minerals are compounds made up of different elements.
-
-
-