Chemistry: Chapter 3 (Atoms Combining) Flashcards
Definition of Element
A substance that contains only one kind of atom and cannot be broken down further into another substance.
Definition of Compounds
A substance that is made of atoms of different elements that are chemically bonded together.
Definition of Mixture
Different substances that are physically mixed together.
What are the 3 signs of chemical change?
- one or more new chemical substances are formed
- energy is taken in or given out during the reaction
- the change is usually difficult to reverse
What are 2 ways to reverse a chemical change?
Heating with carbon and electrolysis
How to differenciate physical changes from chemical changes?
If it produces a new substance, it is chemical change. If it does not, it is physical change.
3 signs of chemical reactions
- colour change
- sweet smell / foul stench
- temperature change
Why do atoms form bonds?
Atms form bonds together in order to obtain a full valence electron shell.
Which group of gases are unreactive?
Group VIII, the noble gases
Why does sodium gain a single positive charge?
When the sodium atom donates an electron, the number of protons is one more than electrons.
What are positive and negative ions called?
Cation (+) and Anion (-)
Why do atoms of Group VIII not form ions?
They have a full electron shell and do not need to receive or donate electrons, they are unreactive.
Definition of Ionic Bond
A strong electrostatic attraction between ions of opposite charge.
Definition of Lattice
3D structure of regular and repeating pattern of oppositely charged ions.
What is the overall charge of the compound NaCl?
No overall charge, the charges on the ions cancel each other out.
Which element goes at the front of a compound name?
The element with a positive charge
Definition of Molecules
Two or more atoms held together by covalent bonds.
Why do carbon atoms not form ions?
Carbon and other elements in Group IV would have to lose or gain many electrons, which would take too much energy, thus carbon only shares electrons.
Why do non-metal elements not form ionic bonds with each other?
Non-metals only receive electrons to form anions, anions will repel each other so it cannot form ionic bonding.
Definition of Covalent Bond
Atoms gaining full electron shells by sharing electrons with each other.
Definition of Regular Lattice
Regular lattice grows in all directions, giving a crystal-like structure.
What is the weak force in between molecultes called?
Intermolecular force
Properties of Ionic Compounds
- high MP and BP
- usually soluble in water
- can conduct electricity when dissolved or molten (ions are not free to move in solid state)
Properties of Covalent Compounds
- low MP and BP
- usually insoluble in water
- cannot conduct electricity (no charge bc no ions)
What are the two types of covalent structures?
Simple molecular structure and giant covalent structure
What are the three giant covalent structures?
Graphite, diamond and silica
Properties of Diamond and Silica
- very hard (held in place by 4 strong covalent bonds)
- high melting point
- cannot conduct electricity (no moving electrons)
Properties of Graphite
- soft and slippery (layers can slide over each other)
- good conductor of electricity (delocalised electrons moving between layers)
Uses of Graphite
- lubricant in engines
- electrodes in electrolysis
Use of Diamond
- tools for drilling and cutting
Uses of Silica
- in bricks for lining furnaces
- sandpaper
Definition of Allotropes
Different forms of an element
Definition of Metallic Bond
The electrostatic attraction between the positive ions in a ‘sea’ of delocalised electron that move freely.
What force are metal ions held together by?
Electrostatic attraction
Properties of Metals
- high melting point (high heat to overcome strong electrostatic forces between metal ions and delocalised electrons)
- malleable and ductile (layers of metal ions can slide over each other)
- good conductors of heat (free electrons take in heat energy, which makes them move faster)
- good conductors of electricity( free electrons move through the lattice as a current of electricity, when a voltage is applied across the metal.
Which metal is the best conductor?
Silver (copper is next but is used more often as it is cheaper)
Which bonds use electrostatic attraction?
Ionic bonding and Metallic bonding
ionic: cation & anion
metallic: positive metal ions & sea of delocalised electrons
What does it mean to be malleable and ductile?
Malleable: can be bent and pressed into shape
Ductile: can be drawn into wires
