Unit 4- atoms combining Flashcards
How many kinds of atoms do an element contain
one
What is a compound
A substance in which two or more elements are chemically combined
Signs of a chemical change
One or more new chemical substances are formed, energy is taken in or given out, usually difficult to reverse
Difference between chemical and physical change
In chemical change, there is new chemical substance formed but not in a physical change
What are ions
Charged particle. It’s charged because it has an unequal number of protons and electrons.
Why do atoms form bonds
Atoms bond with each other in order to gain a stable outer shell
What is an ionic bond
The bond that forms between ions of opposite charge
How is an ionic bond formed
The metal reacts with a non-metal to form an ionic compound. The metal atoms lose electrons. The non-metal atoms gain them. The ions form a lattice of alternating positive and negative ions.
What is an overall charge for a compound
0
Charge of hydroxide ion
1-
Charge of nitrate ion
1-
charge of sulfate ion
2-
charge of carbonate ion
2-
charge of ammonium ion
1+
What is a covalent bond
the chemical bond formed when two atoms share electrons
What is a bond between chlorine molecules
single covalent bond
What is a bond between oxygen molecules
double (covalent) bond
What is a molecule
Group of atoms held together by covalent bonds
Why are forces between particles stronger between ionic compound than covalent compound
In Ionic compound, particles are chared so forces between them are strong, but in a covalent compound is particles are not charged.
Properties of an ionic compound
High melting and boiling point, usually soluble in water, conduct electricity when melted or dissolved in water
Properties of a covalent compound
Low melting and boiling point, tend to be insoluble in water, do not conduct electricity
Why does diamond has a high melting point
Each atom is held in place by four strong covalent bonds
Why can’t diamond conduct electricity
There are no ions or free electrons
What type of structure are diamonds and silicon (iv) oxide
Giant covalent structure ( tetrahedral shape)
What are allotropes
Different forms of the same element
Properties of graphite
Soft because sheets can slide over each other easily. Good conductor of heat and electricity because there are free electrons
What is a metallic bond
The attraction between metal ions and free electrons
Why do metals usually have a high melting point
It takes a lot of heat energy to break up the lattice, with its strong metallic bonds.
Why metals are malleable and ductile
The layers can slide over each other.
Why metals are good conductors of heat
There are free electrons that take in heat energy which makes them move faster, they quickly transfer heat through the metal structure.
Why metals are good conductors of electricity
Free electrons can move through the lattice carrying charge when a voltage is applied across the metal.
