i have essays to write about tomorrow in chemistry. so can someone explain to me about what each one is talking about?
thanks!
1) explain what a mole is and how it is useful in chemistry.
2.) compare and contrast the structure of an oxygen atom, an oxygen ion, and O subscript 2 molecule and hte isotopes O-15 and also O-16. Include information on protons, neutrons, and electrons.
3.) explain how to name compounds. give examples of acids, ionic compounds, molecular compounds, polyatomic ions, and metals with more than one ionization number.
thanks again. :]
1) a mole is just a way to express quantity. 1 mole is just 6.02 x 10^23 of anything, just like how a dozen is 12 of anything.
2) An Oxygen ion has a 2- charge. (two extra electrons) An oxygen atom has two oxygens bonded together with a double bond. (sharing 8 electrons total) And an isotope of 15 is saying you have one less neutron. (check this though)
3) acids: -ic acid. (hydrochloric acid, nitric acid). Ionic compounds: first element name plus second -ide. (sodium chlorIDE) Molecular compounds: use mono, di, tri, etc. water: dihydrogen monoxide) polyatomic ions: you have to remember the anions (phosphates, phosphites, nitrates) and than just write it like ou wold an ionic compound. .
1. Mole is an SI unit and can be defined as the amount of substance.
e.g. 1 mole of one element is equivalent to 1 mole of any other element.
You use moles to find the mass of an atom, the number of particles, and the volume of an atom.
1 mole = 6.02 x 10^23 particles
1 mole = 22.4L
(# of moles)(GMM or GFM or GAM) = weight or mass of the given atom.
GMM, GFM, and GAM are exactly the same thing they are abbreviations for: Gram Molar Mass, Gram Formula Mass, Gram Atomic Mass.
It's basically the total mass of the atom. for instance, H2O would have a GFM, GMM, and GAM of 18grams (you just add the masses of the elements)
2. Oxygen atom is the neutral, balanced element you see on the periodic table
Oxygen atom has a mass of 16g and has 8 neutrons, protons and electrons.
Ions are elements that have lost or gained electrons (i.e. negatively charged or positively charged element)
so, oxygen ion would have 8 neutrons, 8 protons, and 10 electrons (assuming that the mass is still 16). Oxygen has an oxidation state of -2 so when it becomes an ion, it gains 2 electrons.
O2 is a compound. It has a nonpolar covalent bond, it's diatomic, has two oxygen molecules. It still has 1 mole. i think it's double bonded and it's a nonpolar molecule.
isotopes are elements have a change in number of neutrons and mass.
O-15 means it has an atomic mass of 15. the atomic number of oxygen is 8 so 15-8 = 7. O-15 has 7 neutrons, 8 protons and 8 electrons. Number of protons NEVER change.
O-16 has 8 neutrons, 8 protons and 8 electrons.
Atomic mass - atomic number = # of neutrons
Atomic number = # of protons and electrons
3. When you name IONIC compounds, you write the name of the metallic ion as it is and then write the nonmetal ion with an "-ide" ending. Subscripts are always ignored.
example: KCl is called Potassium Chloride.
example2: MgCl2 is called Magnesium Chloride. Notice the ignored subscript 2.
When naming BINARY COVALENT compounds, you follow the ionic compound naming rule BUT you MUST include subscripts in the name
Example: CO is called Carbon Monoxide. Carbon and Oxygen in this case both have an invisible subscript of 1. the prefix mono is used for oxygen but not for carbon because the first element will never include mono.
Example2: SO3 is called sulfur trioxide
ex3: N2O5 is called dinitrogen pentoxide. prefixes are a must for BOTH nonmetals except for when the first nonmetal is only a single atom.
Naming Ions : just add "-ide" ending. you ignore the oxidation states.
F- (the minus is superscript) - flouride
O2- (2- is superscript) - oxide
N3- (superscripted 3-) - nitride
Naming polyatomic Ions: You name them as it is. Polyatomic ions each have their own name which you need a reference table for.
example: KNO3 (subscript 3) is called Potassium Nitrate. You treat the NO3 as one element. NO3 is a polyatomic ion called nitrate.
if you're given the written name then..
ex: Calcium hydroxide is Ca(OH)2 (subscript 2). Calcium is Ca with an oxidation state of +2. Hydroxide is OH with an oxidation state of -1. you put a supscript 2 after OH so it indicates balance. two atoms of OH balances with one atom of Ca. 2 atoms of OH would make it have a -2 charge which balances with the +2 charge from calcium.
ex2: Sodium Cyanide is NaCN. CN is a polyatomic ion called cyanide.
examples of common acids: HCl (hydrochloric acid), HNO3 (nitric acid), H2SO4 (sulfuric acid), H3PO4 (phosphoric acid), H2CO3 or CO2 (carbonic acid), CH3COOH or HC2H3O2 (ethanoic acid/acetic acid)
All of these acids are aqueous solutions meaning they are in liquid form (hence CO2 being an acid rather than the gas).
examples of ionic compounds: NaCl (sodium chloride better known as table salt)
basically a metal + nonmetal. when you write them in using the element symbols, make sure you consider their oxidation states and put the appropriate subscript number beside the appropriate element and use parentheses when necessary.
examples of molecular compounds: molecular compounds also known as polar/nonpolar covalent compounds or binary covalent etc etc.
basically a compound made of two nonmetals. H2O is a molecular compound. Once again, consider their oxidation states and use the appropriate subscripts.
examples of polyatomic ions: i named a few above.
metals with more than one "ionization number": i use the term oxidation number/state. Most transition metals have more than one oxidation state. Some nonmetals have more than one. Just look at a periodic table. The numbers on the top right hand corner are oxidation numbers. Transition metals are the metals from groups 3 - 12