Atoms, elements and compounds Flashcards
Define an element?
Is a pure substance that cannot be broken down by any physical or chemical means into simpler substances
Define compound?
Are two or more elements chemically bonded together.
Define mixtures?
Is the combination of two or more substances that are not chemically combined.
Define isotopes?
Isotopes are atoms with the same element and atomic number but with different mass numbers.
Define relative atomic mass?
Is the average mass of the isotope of an element compared to 1/12th of the mass of an atom of carbon 12.
Define the octet rule?
Refers to the tendency of atoms to prefer to have 8 electrons in the valence or the outermost layer or last shell
Define valency?
Valency is the maximum number of electrons which an atom can gain or lose.
Define radioactive Isotopes?
They are unstable due to the imbalance of protons and neutrons so in order attain stability it will emit energy in the form of radiation.
What are the uses of radioactive Isotopes?
- for treatment of cancer (Co 16)
- to locate tumors (iodine 131)
- for carbon dating (C 14)
- used as tracers to detect leaks in oil and gas pipes.
- used to sterilise things.
Define Ionic bond?
It is the complete transfer of electron from one atom to another atom.
- this bond only form between metal and non-metal atoms.
Define the properties of Ionic bond?
- exists is solid state
- usually soluble in water
- have high melting and boiling point
- they are good conductors of electricity in molten state or in solution.
- Bad conductors in solid.
Define covalent bond?
This bond is When a chemical bond is formed between between two atoms by sharing of electrons to gain the nearest noble gas configuration.
What are the Properties of covalent bond?
- exist in liquid and gaseous state.
- they are in-soluble in water.
- they have low melting and boiling point.
- they do not conduct electricity in molten state and in liquid.
