1. Non-zero digits are always significant.
2. Any zeros between two non-zero digits are significant.
3. A final zero or trailing zeros in the decimal portion ONLY are significant.

Rules for Using Significant Figures: For addition and subtraction:

Rules for Using Significant Figures:

For multiplication and division:

 the answer should have the same number of significant figures as the term with the fewest number of significant figures.

Rules for Using Significant Figures:

In multi-step calculations:

 you may round at each step or only at the end.

Rules for Using Significant Figures: Exact numbers, such as integers, are treated as if...

...as if they have an infinite number of significant figures.

Rules for Using Significant Figures:

In calculations, round up if : 

 round down if:

 If the first discarded digit is 5, then round up if: 

 round down if:

In calculations, round up if the first digit to be discarded is greater than 5 and round down if it is below 5.

If the first discarded digit is 5, then round up if a nonzero digit follows it, round down if it is followed by a zero.

Significant Figures: Addition and Subtraction:

 12.793 + 4.58 + 3.25794 = 20.63094

sig figs?

With significant figures it is 20.63 since 4.58 has 2 decimal places, which is the least number of decimal places.

56.937/0.46 = 130.29782609

sig figs?

With significant figures, the final value should be reported as 1.3 x 10² since 0.46 has only 2 significant figures. Notice that 130 would be ambiguous, so scientific notation is necessary in this situation.

Even though the _____ occupy most of the volume of the atom, they hold only a _____percentage of the atom's mass.

The _____is incredibly dense and contains almost all of the mass of the atom. Actually nuclear densities are approximately 10¹⁴ times that of normal matter.

electrons occupy most of the volume of the atom, they hold only a very small percentage of the atom's mass.

 The nucleus is incredibly dense and contains almost all of the mass of the atom. Actually nuclear densities are approximately 10¹⁴ times that of normal matter.

The ____/____occupies the majority of the atom.

 This ___ is actually over __% of the volume of the atom.

The electron cloud occupies the majority of the atom. This cloud is actually over 99% of the volume of the atom.

Masses of Atomic Components

in kg:

p⁺, proton mass:

n^o, neutron mass:

e^-, electron mass:

Masses of Atomic Components

p⁺, proton mass: 1.67262 x 10^-27 kg
n^o, neutron mass: 1.67493 x 10^-27 kg
e^-, electron mass: 9.1094 x 10^-31 kg

This is the total number of protons plus the number of neutrons (i.e., the total number of nucleons).

(A = # of protons + # of neutrons)

Z=is the number of protons.

The atomic number often is not included because the element name (or element symbol) also tells the number of protons.

If the number of protons changes, then it becomes a different element.

For example, helium will always have 2 protons; if you add a proton then it becomes lithium (Li).

 the number of protons.

However if the atom has a non-zero charge, the number of electrons does not equal Z, and the atom is referred to as an ion.

 There are 35 protons, 45 neutrons and since it is neutral there are 35 electrons.

1. Ion Formation (Ionization)

2. Isotope Conversion

3. Transmutation

E=mc^2

E=

m=

c=

E=nuclear binding energy

m=mass (in the case of nuclear binding energy equation it is the missing mass)

c=speed of light, 2.9979*10^8 m/s

i=an index identifying each isotope for the element

f=fractional abundance of isotope i

m=mass of isotope i