a few questions for all you guys

[Ice_Phoenix87]

1.can anyone identify the difference between elements, compounds and mixtures in terms of particle theory.

 

2. describe the phyiscal properties used to classify compounds as ionic or covalent molecular or covalent network.

 

3. describe using diagrams ionic compounds in terms of repeating three-dimensional lattices of ions.

 

4. identify which elements exist as molecules or as covalent lattices

thanks guys

it will really help me. hopefully i am not asking to much

[aommaster]

1. An element is a substance that contains only ONE type of atom. A compound is a mixture of two or more elements THAT HAVE BEEN CHEMICALLY BONDED together. A mixture is just a mixture of two or more elements, without the bonds.

 

2.An ionic subtance conducts electricity when molten or dissolved in a solution. A covalent subtance that is molecular has a low melting point. I don't really know what is covalent network.

 

3. I don't know

 

4. I don't know

[aommaster]

I have something to add to that. A covalent network is also called 'Giant Covalent'.

It is subtances that have high melting point, and do not conduct electricity NO MATTER WHAT HAPPENS TO THEM (melted etc.)

 

Examples of these are diamond and silicon dioxide

[Gampin]

4) Elements as molecules : Noble gases and H2

 

Covalent lattices :

 

I think this is what you mean.

 

http://www.molecules.org/elements.html

[researcher88]

1.can anyone identify the difference between elements, compounds and mixtures in terms of particle theory.

 

An element is a pure substance which cannot be decomposed into simpler substances.

 

A compound is a pure substance which can be decomposed into simpler substances. For example, NaCl----->Na+Cl

 

A mixture can be seperated into two or more pure substances by physical or mechanical means such as filtering, boiling or using a magnet or tweezers.

--------------------------------------------------------------------------

2. describe the phyiscal properties used to classify compounds as ionic or covalent molecular or covalent network.

 

 

Ionic (a metal and a non-metal)

1) High melting and boiling points.

2) Conducts electricity only in molten or dissolved form.

3) Hard and brittle.

4) Electrostatic forces holds the particles together in the solid.

Chemical examples:

NaCl, CuSO4, (NH4)2SO4, Ca(OH)2, FeCl.

--------------------------------------------------------------------------

Covalent

1) High melting and boiling points.

2) on electrical conductivity.

3) Hard and brittle

4) Covalent bonding throughout the crystal

Chemical example:

Sio, Diamond

NOTE: Graphite is covalent but it conducts electricity.

--------------------------------------------------------------------------

3. describe using diagrams ionic compounds in terms of repeating three-dimensional lattices of ions.

 

When sodium is burned in a chlorine atmosphere, it produces the compound sodium chloride. This has a high melting point (800 ºC) and dissolves in water to to give a conducting solution therefore sodium chloride is an ionic compound.

Electrostatic attraction are in these oppositely charged ions packing together in a lattice. The attractive forces holding the ions in place can be referred to as ionic bonds. (i think thats what you're asking for)

--------------------------------------------------------------------------

 

Hope i helped