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Atoms, Elements and Compounds
- ATOMS are incredibly SMALL, and make up EVERYTHING in the universe.
- They are the SMALLEST part of an ELEMENT that can exist.
- They are composed of THREE even smaller particles known as SUB-ATOMIC PARTICLES: PROTONS, NEUTRONS, and ELECTRONS.
- At the center of an atom lies the NUCLEUS, containing PROTONS and NEUTRONS.
- PROTONS have a positive charge (+1) and a relative mass of 1.
- NEUTRONS have no charge (0) and a relative mass of 1, similar to protons.
- ELECTRONS orbit around the nucleus in electron shells.
- They are negatively charged (−1) and are VERY SMALL, with virtually no mass when compared to protons and neutrons.
- The NUCLEUS is tiny compared to the whole atom, about 1/10,000th of the atom's total size, but it holds nearly ALL the atom's mass.
Radius of an ATOM: 0.1nm (1 x 10-10 m)
Radius of a NUCLEUS: 1 x 10-14 m
- Atoms are NEUTRAL and have NO OVERALL CHARGE.
- This is because they have the SAME NUMBER OF PROTONS AND ELECTRONS, which CANCELS OUT THEIR CHARGES.
Chemical Symbols
- Atoms of each element are represented by a CHEMICAL SYMBOL which can be found in the PERIODIC TABLE. E.g. Carbon has the symbol C.
- They can be represented as below:
- The ATOMIC NUMBER indicates how many protons are in an atom's nucleus.
- The MASS NUMBER is the total count of both protons and neutrons.
- To find the number of NEUTRONS, SUBTRACT the atomic number from the mass number.
Elements:
- An ELEMENT is a substance made up of ONE TYPE OF ATOM.
- There are over 100 different discovered ELEMENTS which can all be found in the PERIODIC TABLE.
- All the atoms in an element contain the SAME NUMBER of PROTONS in their nucleus.
- When atoms have different numbers of PROTONS, they are classified as DIFFERENT elements.
- This means the ATOMIC NUMBER determines the ELEMENT of an atom. For example, Carbon atoms ALWAYS have 12 protons (has an atomic number of 12).
Isotopes
- All atoms of a particular ELEMENT have the same ATOMIC NUMBER but may have different numbers of NEUTRONS.
- ISOTOPES are different forms of the same element, having the SAME NUMBER OF PROTONS (same atomic number) but DIFFERENT NUMBERS OF NEUTRONS (different mass numbers).
- A common example is Carbon-12, Carbon-13 and Carbon-14 which all have six protons but differ in the number of neutrons:
Compounds
- COMPOUNDS are substances that form when two or more elements react and their atoms combine.
- These elements join in FIXED PROPORTIONS and are held together by CHEMICAL BONDS.
- In compounds, only the ELECTRONS are involved in bond formation while the nuclei remain unchanged.
- The PROPERTIES of a compound are usually quite different from the properties of the original elements.
- For example, HYDROGEN is a colorless, odourless gas that is highly flammable, while OXYGEN is a colorless gas that can burn (combustion). When these two elements react, they form WATER (H₂O) which is a liquid at room temperature and does NOT BURN. The properties of water are entirely different from those of its constituent gases, hydrogen and oxygen.
Compound Formulas
- FORMULAS represent compounds and show the elements and the number of atoms of each element in a compound.
- The formula for water is H₂O, indicating 2 hydrogen atoms and one oxygen atom.
- Some familiar compounds and their formulas include:
Atoms, Elements and Compounds
- ATOMS are incredibly SMALL, and make up EVERYTHING in the universe.
- They are the SMALLEST part of an ELEMENT that can exist.
- They are composed of THREE even smaller particles known as SUB-ATOMIC PARTICLES: PROTONS, NEUTRONS, and ELECTRONS.
- At the center of an atom lies the NUCLEUS, containing PROTONS and NEUTRONS.
- PROTONS have a positive charge (+1) and a relative mass of 1.
- NEUTRONS have no charge (0) and a relative mass of 1, similar to protons.
- ELECTRONS orbit around the nucleus in electron shells.
- They are negatively charged (−1) and are VERY SMALL, with virtually no mass when compared to protons and neutrons.
- The NUCLEUS is tiny compared to the whole atom, about 1/10,000th of the atom's total size, but it holds nearly ALL the atom's mass.
Radius of an ATOM: 0.1nm (1 x 10-10 m)
Radius of a NUCLEUS: 1 x 10-14 m
- Atoms are NEUTRAL and have NO OVERALL CHARGE.
- This is because they have the SAME NUMBER OF PROTONS AND ELECTRONS, which CANCELS OUT THEIR CHARGES.
Chemical Symbols
- Atoms of each element are represented by a CHEMICAL SYMBOL which can be found in the PERIODIC TABLE. E.g. Carbon has the symbol C.
- They can be represented as below:
- The ATOMIC NUMBER indicates how many protons are in an atom's nucleus.
- The MASS NUMBER is the total count of both protons and neutrons.
- To find the number of NEUTRONS, SUBTRACT the atomic number from the mass number.
Elements:
- An ELEMENT is a substance made up of ONE TYPE OF ATOM.
- There are over 100 different discovered ELEMENTS which can all be found in the PERIODIC TABLE.
- All the atoms in an element contain the SAME NUMBER of PROTONS in their nucleus.
- When atoms have different numbers of PROTONS, they are classified as DIFFERENT elements.
- This means the ATOMIC NUMBER determines the ELEMENT of an atom. For example, Carbon atoms ALWAYS have 12 protons (has an atomic number of 12).
Isotopes
- All atoms of a particular ELEMENT have the same ATOMIC NUMBER but may have different numbers of NEUTRONS.
- ISOTOPES are different forms of the same element, having the SAME NUMBER OF PROTONS (same atomic number) but DIFFERENT NUMBERS OF NEUTRONS (different mass numbers).
- A common example is Carbon-12, Carbon-13 and Carbon-14 which all have six protons but differ in the number of neutrons:
Compounds
- COMPOUNDS are substances that form when two or more elements react and their atoms combine.
- These elements join in FIXED PROPORTIONS and are held together by CHEMICAL BONDS.
- In compounds, only the ELECTRONS are involved in bond formation while the nuclei remain unchanged.
- The PROPERTIES of a compound are usually quite different from the properties of the original elements.
- For example, HYDROGEN is a colorless, odourless gas that is highly flammable, while OXYGEN is a colorless gas that can burn (combustion). When these two elements react, they form WATER (H₂O) which is a liquid at room temperature and does NOT BURN. The properties of water are entirely different from those of its constituent gases, hydrogen and oxygen.
Compound Formulas
- FORMULAS represent compounds and show the elements and the number of atoms of each element in a compound.
- The formula for water is H₂O, indicating 2 hydrogen atoms and one oxygen atom.
- Some familiar compounds and their formulas include:
