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REMEMBER: Number of protons is the same as asking for atomic number!
# Neutrons = Mass Number - Protons (Atomic Number)
Number Electrons = Atomic Number - charge number (if charge is a positive number)
Number Electrons = Atomic Number + charge number (if charge is a negative number)
Memorize that H, N, O, F, Cl, Br, I are all diatomic molecules
How many electrons does magnesium, Mg, need to lose to have the same number of electrons as one of the noble gases?
Mg is in group 2A so it has extra 2 valence electrons, by losing 2 losing electrons it can become stable as a noble gas.
If you remove 2 electrons from Mg then it has equal number of electrons to Ne
Group 1A elements are always = +1 (this means they lose 1 electron to be electronic to a noble gas)
According to the chart above Group 7A gain 1 electron because their charge is -1
Typically the number of electrons an atom has is equivalent to the number of protons an atom has (the exception to this rule are ions or unstable atoms but for all intensive purposes unless otherwise stated assume the atoms stability).
Number of electron = atomic number + charge (additional electrons)
18 electron = 16 + 2
Ca: Atomic Number = 20
If Ca loses 2 electrons then Ca has 18 electrons
Phosphorus Atomic Number : 15 (so there are 15 electrons/protons)
Which element has 11 protons?
Refer to the periodic table in the next question for this and the following questions.
The mass of 1 Li atom: 1 atom x 6.94(g/mol) x (1 mol / 6.022E23 atom) = 1.15E-23g
Which of the following elements are diatomic molecules at room temperature?
(All answers must be correct to get credit.)
Prefixes used in naming molecular compounds (compounds made from nonmetals).
1 mono- CO is carbon monoxide
2 di- SO2 is sulfur dioxide
3 tri- SO3 is sulfur trioxide
4 tetra- CCl4 is carbon tetrachloride
5 penta- PCl5 is phosphorus pentachloride
6 hexa- SF6 is sulfur hexafluoride
The ending of the second element is dropped and replaced with "ide".
Atoms can only gain or lose a few electrons to be isoelectronic with a noble gas.
Isoelectronic meaning that when compared both atoms have the same number of electrons.
Mg is closest to Ne, and in order to be isoelectronic it must lose 2 electrons.
Let's take for example Na (sodium) for it to be isoelectronic with a noble gas (specifically Ne) it must lose one electron.
Lets take for example F (fluorine) for it to be isoelectronic with a noble gas (specifically Ne) it must gain one electron
Which statements are correct about MgCl2? (All correct answers must be selected for credit.)
Ionic compounds are all solids at room temperature. They consist of positive and negative ions held together by strong electrostatic forces.
For example, NaCl consists of positive sodium ions (Na+) attracted to negative chloride ions (Cl-). NaCl is not a molecule, but consists of many sodium and chloride ions attracted to each other in the solid.
Ionic compounds (a metal and a nonmetal) are named using the name of the metal followed by the name of the nonmetal with its ending dropped and replaced with ide.
NaCl is sodium chloride,
MgCl2 is magnesium chloride, and
MgO is magnesium oxide.
S is below O on the periodic table. So, like O, it gains 2 electrons to be isoelectronic with a noble gas.
S like O gains 2 electrons to be isoelectronic with a noble gas.
What is the mass of one molecule of carbon monoxide, CO in u, amu, or atomic mass units? Use 4 SIG. FIG.
The number under the element symbol has 3 related meanings. The first 2 are:
(1) It gives the relative average mass of the elements. For example, the Be atom (9.0122) is about 9 times the mass of the H atom (1.0079) and slightly less than half the mass of the F atom (18.9984).
(2) It is the actual mass of the elements in atomic mass units (amu or simply u). 1 Carbon-12 (6 protons and 6 neutrons) atom is defined to be exactly 12 u. [The mass of C given in the periodic table is slightly larger because it is the average mass of all the C isotopes--same number or protons but different numbers of neutrons. Most C is carbon-12, but there is a small amount of carbon-14 (6 protons and 8 neutrons).] Examples, what are the masses of the following molecules to 4 significant figures in u?
The nitrogen molecule, N2: 2 x 14.00 u = 28.00 u
Carbon dioxide, CO2: 12.01 + 2 x 16.00 = 44.01 u
The number under the element symbol has a third meaning. This is the most common meaning. It is the mass in grams of 1 mole of the element. A mole is a number just like a dozen or a million. However, a mole is a very big number. It is 6.02 x 1023 (almost a trillion trillions or 1024). This number is called Avogadro's number. Thus, 1 mol of O atoms has a mass of 15.9994 g or 16.00 g to 4 significant figures.
What is the mass of a mole (abbreviated mol) of the following molecules to 4 significant figures grams (g)?
Carbon dioxide- CO2: 12.01 + 2 x 16.00 = 44.01 g/mol (grams per mole)
Water- H2O: 2 x 1.008 + 16.00 = 18.02 g/mol
CO- 12.02 + 16 = 28.01
C2H6- 2(12.01) +6(1.008) = 30 g/mol
NH4Cl = 14 + 4(1) +35
1 carbon-12 atom is 12 u.
Iron (II) = Fe 2+
FeCl2 (charges have to balance out)
2+ + 2(1-)=0
(II) tells you that Iron has a 2+ charge.
Ammonium ion: NH4+
Nitrate ion: NO3-
Sulfate ion: SO42- ; Hydrogen sulfate ion: HSO4-
Hydroxide ion: OH-
Cyanide ion: CN-
Phosphate ion: PO43-; Hydrogen phosphate ion: HPO42-; Dihydrogen phosphate ion: H2PO4-
Carbonate ion: CO32-; Hydrogen carbonate ion: HCO3-
Acetate ion: CH3COO-
Permanganate ion: MnO4-
Oxide ion: O2- (not polyatomic ion); Peroxide ion: O22-
(III) tells you that Fe has a 3+ charge
Carbonate ion: CO32-