Chemical compounds

Learning goals We are learning about chemical compounds. We are learning to identify parts of chemical formulas. We are learning to identify two types of chemical compounds.

Chemical compounds Formed from elements in periodic table Formed from 2 or more elements We use them in every day life!

Chemical compounds Have an official name and a chemical name Can be identified by words and symbols

reactivity The closer to an atom is to a full outer electron shell, the more reactive it is How likely an atom will take part in a chemical reaction and form a compound The atoms of group 18 are not reactive at all Noble gases Full outer electron shell

Try this Name the least reactive group of elements. Why? Nobel gases! Full outer shell! Name the two most reactive. Why? Alkali (grp 1) and Halogens (grp 17). One electron away from noble gas! Name the element in each pair that is more reactive: Na and Mg S and Cl K and Na F and Cl

Chemical formulas A group of letters and subscript numbers that represent the make-up of a chemical compound H2O symbol for element hydrogen symbol for element oxygen No small number here means 1 atom of oxygen Small number here means 2 atoms of hydrogen

Try this CaCO3 Na3PO4 MgCl2 NaC5H8NO4 H2O2 C6H12O6 CO2 CCl2F2 CH2F2

Please complete What does the subscript in a chemical formula tell you? What does no subscript mean? For the compound ammonia, NH4, how many nitrogen atoms are there, and how many hydrogen atoms are there in each molecule? Write a chemical formula for a compound that is made of one atom of carbon (C) and 4 atoms of hydrogen (H)? Write the chemical formula for a compound that has two atoms of nitrogen and four atoms of oxygen.

stability When elements form compounds, they become more stable. All elements try to achieve a full, stable outer electron shell that noble gases have.

stability Elements achieve a full shell in one of three ways: Metals lose electrons to form positive ions. Non-metals gain electrons to form negative ions. Non-metals share electrons.

ions An atom or group of atoms that has an electrical charge. Can be either positive or negative.

Types of compounds Two types: Ionic Molecular

Ionic compounds Metal ions are positively charged Non metal ions are negatively charged Ionic compounds form because metal ions and non-metal ions are attracted to each other.

Ionic properties Solid at room temperature Very high melting points Conduct electricity when melted or dissolved in water

Molecular compounds Non-metal atoms can share electrons with other non-metal atoms Hydrogen is included here

Molecular properties Solids, liquids, or gases at room temperature Lower melting points than ionic compounds Do not conduct electricity when melted or dissolved in water

Ionic or molecular NaCl CH4 CO CaCl2 C12H22O11 CCl4 CaO MgO CuBr2 CH3OH

Learning goals We are learning about chemical compounds. We are learning to identify parts of chemical formulas. We are learning to identify two types of chemical compounds.