An atom is the smallest part of an element that can exist
An element is a substance of only one type of atom
Elements are listed in the periodic table; there are approximately 100
Elements can be classified into two groups based on their properties: metals and non-metals
Elements may combine through chemical reactions to form new products called compounds
A compound is two or more elements combined chemically in fixed proportions which can be represented by formulae
Compounds do not have the same properties as their constituent elements
A mixture consists of two or more elements or compounds not chemically combined together; it does have the same chemical properties
Methods to separate mixtures without involving chemical reactions are:
Filtration
Crystallisation
Simple distillation
Fractional distillation
Chromatography
Simple distillation separates liquid from a solution by boiling off the liquid, condensing it, and reading the boiling point of the pure liquid
Crystallisation/evaporation separates a solid dissolved in a solvent by heating the solution until the solvent evaporates, leaving the solid behind
Fractional distillation separates a mixture of liquids based on their different boiling points using a fractionating column
Filtration separates an insoluble solid suspended in a liquid by catching the solid in the filter paper
Chromatography separates a mixture of substances dissolved in a solvent by allowing the solvent to rise on a piece of paper, separating the mixture into components
A separating funnel is used to separate immiscible liquids based on their different densities
The plum-pudding model describes the atom as a ball of positive charge with negative electrons embedded in it
The Bohr/nuclear model suggests electrons orbit the nucleus at specific distances and came about from alpha scattering experiments
Protons are smaller, positive particles discovered in the nucleus through later experiments
James Chadwick's work provided evidence for the existence of neutrons in the nucleus
The structure of an atom includes a small central nucleus made up of protons and neutrons, surrounded by electrons
Relative masses and charges of proton, neutron, and electron:
Masses: 1, 1, very small
Charges: 1, 0, -1 (respectively)
Atoms are electrically neutral because they have an equal number of protons andelectrons
Atoms are electrically neutral because they have the same number of electrons andprotons
The radius of an atom is 0.1 nm
The radius of a nucleus is 1 x 10^-14 m, which is 1/10000 the size of the atom
The number of protons in the nucleus is called the atomic number
Atoms of the same element have the same number of protons in the nucleus, which is protons
The majority of the mass of an atom is in the nucleus
The mass number is the total number of protons and neutrons
To calculate the number of neutrons, subtract the atomic number from the mass number
An isotope is atoms of the same element with a different number of neutrons; isotopes of the same element have the same chemical properties as they have the same electronic structure
The relative atomic mass is the average mass value that considers the mass and abundance of isotopes of an element, based on a scale where the mass of 12C is 12
Electronic configurations of He (2), Be (4), F (9), Na (11), and Ca (20) are:
He: 2
Be: 2,2
F: 2,7
Na: 2,8,1
Ca: 2,8,8,2
These configurations demonstrate how shells are occupied by electrons
Ions are charged particles formed when atoms lose electrons (positive ions) or gain electrons (negative ions)
Properties of metals and non-metals:
Metals have high boiling/melting points, conduct heat and electricity, are shiny, malleable, have high density, and form basic oxides
Non-metals have low boiling/melting points, don't conduct heat or electricity (except graphite), are dull, brittle, have low density, and form acidic oxides
When a metal reacts with a non-metal, an ionic compound (made of positive and negative ions) is formed
When a non-metal reacts with a non-metal, a molecular compound containing covalently bonded atoms is formed, where atoms share electrons
Solute is a substance dissolved in a solvent to form a solution. Miscible substances mix, while immiscible substances don't. Soluble substances dissolve, while insoluble substances don't
The columns of the periodic table are called groups