Exploring Earth’s Past. 3 Basic Types of Rocks. Igneous Crystalline Cooling and hardening of magma Make up the majority of crust E.g., pumice Sedimentary result of the accumulation of small pieces broken off of pre-existing rocks
Exploring Earth’s Past
u = atomic mass unit (1 u = 1.67 x 10-24 g)
So, mass number (A) = #p+ + # n0
The mass number of an element is represented as relative mass numbers
since the atoms are so small. The scale used is that of C-12 (C-12 = 12u).
Standard Atomic Notation: AX
Notice the masses in the periodic table!
They are not integers!
The masses found in the periodic table are actually called atomic masses. They are weighted average of the mass numbers of the atoms of an element.
Atoms of an element have different number of neutrons. They have the same number of protons, because Z is unique to the element
Isotopes are forms of an element in which the atoms have the same number of protons but different number of neutrons.
Atomic mass = 75.77% x 35 + 24.23% x 37 = 35.45
Protons and electrons are largely responsible for the chemical behaviour
of an element, therefore isotopes may have the same chemical properties.
But physical properties may vary. E.g., heavy water (H-2 aka deuterium)
Is used in nuclear reactors.