Atoms, Ions and Molecules. Chapter 2. Dalton’s Atomic Theory (1808). All matter is composed of extremely small particles called atoms Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
2. Atoms of the same element are identical and atoms of a different element have different masses and chemical properties.
4. Chemical reactions involve the rearrangement of atoms. No new atoms are created or destroyed.
X-rays give some drops a charge.
Some drops would hover
From the mass of the drop and the charge on
the plates, he calculated the mass of an electron
9.11 x 10-28
1.67 x 10-24
1.67 x 10-24
Atomic number (Z) = number of protons in nucleus
Mass number (A) = number of protons + number of neutrons
= atomic number (Z) + number of neutrons
Isotopes are atoms of the same element (X) with different numbers of neutrons in their nuclei
Mass spectrum of chlorine. Elemental chlorine (Cl2) contains
only two isotopes: 34.97 amu (75.53%) and 36.97 (24.47%)
AAM = (34.97 amu)(0.7553) + (36.97 amu)(0.2447)
AAM = (26.412841 amu) + (9.046559 amu)
AAM = 35.4594 amu
Alkali Earth Metal
Atoms are electrically neutral.
Same number of protons and electrons.
Ions are atoms, or groups of atoms, with a charge.
Has gained one electron
Has gained two electrons
Has lost one electron
Has lost two electrons
Types of elements
Metal and Nonmetal
Solid, liquid or gas
Shows the kind and number of atoms in the smallest piece of a substance.
Molecular formula- number and kinds of atoms in a molecule.
For most of the Group A elements, the Periodic Table can tell what kind of ion they will form from their location.
Elements in the same group have similar properties.
Including the charge when they are ions.
Copper (II) ion
Chromium (VI) ion
Mercury (II) ion
Anions are always the same.
Change the element ending to – ide
Hydronium H3O +
Chlorite ClO2 -
Binary Compounds - 2 elements.
Ionic - a cation and an anion.
To write the names just name the two ions.
Easy with Representative elements.
NaCl = Na+ Cl- = sodium chloride
MgBr2 = Mg+2 Br- = magnesium bromide
The problem comes with the transition metals.
Need to figure out their charges.
The compound must be neutral.
same number of + and – charges.
Use the anion to determine the charge on the positive ion.
Write the name of CuO
Need the charge of Cu
O is -2
copper must be +2
Copper (II) oxide
Cl is -1 and there are three of them = -3
Co must be +3 Cobalt (III) chloride
Write the name of Cu2S.
Since S is -2, the Cu2 must be +2, so each one is +1.
copper (I) sulfide
Each O is -2
Fe must be = + 3
iron (III) oxide
Write the names of the following:
Will have polyatomic ions
At least three elements
name the ions
The charges have to add up to zero.
Get charges on pieces.
Cations from name of table.
Anions from table or polyatomic.
Balance the charges by adding subscripts.
Put polyatomics in parenthesis.
Write the formula for calcium chloride.
Calcium is Ca+2
Chloride is Cl-1
tin (II) oxide
tin (IV) oxide
Copper (II) sulfate
Iron (III) phosphide
Iron (III) sulfide
made of just nonmetals
smallest piece is a molecule
can’t be held together because of opposite charges
can’t use charges to figure out how many of each atom
One exception is we don’t write mono- if there is only one of the first element.
Compounds that give off hydrogen ions when dissolved in water
Must have H in them (somewhere)
will always be some H next to an anion
The anion determines the name.
If the anion attached to hydrogen ends in -ide, put the prefix hydro- and change -ide to -ic acid
HCl - hydrogen ion and chloride ion
H2S hydrogen ion and sulfide ion
If the anion has oxygen in it
it ends in -ate or -ite
change the suffix -ate to -ic acid
HNO3 Hydrogen and nitrate ions
change the suffix -ite to -ous acid
HNO2 Hydrogen and nitrite ions
Hydrogen will always be first
name will tell you the anion
make the charges cancel out.
Starts with hydro- no oxygen, -ide
no hydro, -ate comes from -ic, -ite comes from -ous