Bonding and calculations Flashcards
What is the mass number?
the total number of protons and neutrons
What is the atomic number?
the number of protons (which also equals the number of electrons)
What is an element?
an element is a substance consisting of atoms
What is a compound?
compounds are formed when atoms of two or more elements are chemically combined together.
What are isotopes?
isotopes are different atomic forms of the same element, which have the same number of protons but a different number of neutrons.
What is ionic bonding?
Ionic bonding is when atoms lose or gain electrons to form charged particles called ions, they are then strongly attracted to one another because of their opposite charges, forming an ionic bond.
What groups in the periodic table lose electrons and what groups gain electrons?
Groups 1,2 and 3 loose electrons to obtain a full outer shell and become positive ions.
groups 5,6 and 7 gain electrons to obtain a full outer shell and become negative ions.
Metals lose electrons and Non-metals gain electrons.
What properties to ionic compounds have?
- giant ionic lattice
- regular arrangement
- strong forces of attraction between oppositely charged ions
- high melting/ boiling points due to strong attraction between ions. Therefore needs a large amount of energy to overcome this attraction.
- do not conduct electricity as solid but do when melted or dissolved in water because the ions are free to move so they’ll carry an electrical current.
What is covalent bonding?
covalent bonding is when atoms share electrons to obtain a full outer shell, they only share electron in their highest energy levels and it occurs between two nonmetals.
What are the two kinds of covalent substances?
simple molecules or giant structures.
Explain the properties of simple molecular covalent substances.
The atoms form very strong covalent bonds to form small molecules of several atoms. The bonds between atoms may be strong but they have very weak intermolecular forces which means that they have a low melting/ boiling points because they molecules are easily broken.
They do not conduct electricity because there are no ions so there’s no electrical charge.
Explain the properties of giant covalent structures.
- regular lattice with no charged ions.
- all the atoms are bonded to each other by strong covalent bonds
- this means they have a very high boiling/melting point
- they do not conduct electricity because they have no charge.
Give three examples of giant covalent structures and state their properties.
Diamond- each carbon atom forms four covalent bonds forming a very rigid covalent structure hence diamond is the hardest natural substance on earth.
Silicon Dioxide- the same structure as diamond but rather than carbon atoms each silicon atom is covalently bonded to four oxygen atoms.
Graphite- each carbon atom forms three covalent bonds, this creates layers which are free to slide over each other hence graphite is soft and slippery because of its weak intermolecular forces between the layers.
graphite is the only covalent structure that conducts electricity because each carbon atom has one delocalised electron which can move and pass on a current.
Describe the structure of a metal.
- Metals have a giant structure, they consist of positive ions with a sea of delocalised electrons, these free electrons can move through the whole structure and so metals are good conductors of heat and electricity.
- strong forces between atoms due to opposite charges attracting
- electrons allow the layers of atoms to slide over each other allowing metals to be bent and shaped.
What are smart materials?
smart materials behave differently depending on the conditions
