Unit 1: The Atom Flashcards
Atomic Theory explains …
Explains law of
- Conservation of Matter
- Definite Proportions – elements combine in definite, fixed ratios
- Constant Composition – for all samples of compound, same element composition by mass
- Multiple Proportions – the same elements can combine in multiple different ratios to form different compounds
Atomic Theory allows
Allows stoichiometry:
- composition stoichiometry – mass relations within a substance.
- reaction stoichiometry – mass relations between substances in a reaction.
Composition of the atom
Protons
Neutrons
Electrons
Are atoms usually postive negative or neutral?
What gives an atom its properties?
What are atoms Identified by?
Usually neutral; can buildup (static); try to equalize charge
Ratios of the three particles give atom its properties
ID by proton - unchanging
Nuclear Theory
Matter not uniform
- Most mass, all + charge in central nucleus
- Mostly empty space – negative electrons dispersed
- Number of negative electrons = positive protons
What comprises 99.9% of atom’s mass ?
Nucleus
How many identifiable elements are there?
How many are synthetic?
118 Identifiable elements
20 synthetic
Elemental Symbol
- one or two letter abbreviation used to represent an element
- Some first two letters - F, Ne, O, Si, C
- Some one or two letters not first – Zn, Cl
- Some ancient name
- Au (aurum)
- Pb (plumbum)
- W (wolfram)
- K (kalium)
- Na (natrium)
Atomic Number
the number of protons contained within an atom’s nucleus
Mass number
the sum of the number of protons and neutrons contained within an atom’s nucleus.
Write the nuclide symbol for each of the following elements:
An element with 6 protons, 6 neutrons and 6 electrons
An element with 9 protons, 10 neutrons and 9 electrons
An element with 20 protons, 21 neutrons and 20 electrons
Ion
a charged atom
Cation
an ion with positive charge
