Chapter 1 - Atomic Theory Flashcards
What is mass number?
Mass number = atomic number + number of neutrons
What is the atomic number?
The number of protons in an atom
What is an isotope?
An element that has atoms with different mass numbers.
Atoms that have the same number of protons as one another but different numbers of neutrons. (Same atomic mass but with different mass numbers)
What are ions?
Electrically charged species formed when atoms gain or lose electrons.
Define cation and how are they formed?
A positively charged atom.
When one or more electrons are removed from an atom
Define anion
And how are they formed?
Negatively charged atoms
When an atom gains one or more electrons.
What is electron configuration?
The arrangement of electrons in shells,
Eg. The electron configuration of an atom with 2 electrons in the first shell, 8 electrons in the second shell, and 3 in the third, it would be written 2, 8, 3.
What is a valence electron?
The electrons in the outer shell of an atom.
Give an example of a valence electron.
Sodium electron configuration:
2, 8, 1, has one valence electron.
Oxygen electron configuration:
2, 6, has six valence electrons.
Define element
Elements are substances composed of only one type of atom.
Define compound
Substances composed of two or more different types of atoms, strongly bonded together in fixed proportions.
Eg. Water and copper oxide.
Explain the vertically arranged elements
When elements are ordered vertically, they share similar outer energy shell electron configurations.
Eg. Group 1 elements contain 1 valence electron.
Similar valence configuration results in similar chemical properties.
Eg. Group 1 elements are all soft, reactive metals.
Explain the horizontally arranged elements
Called periods.
The period number corresponds to the number of the shell in which the outermost electrons are located in the neutral atoms.
Eg. Lithium, with an electron config. of 2, 1, has its outermost in the second shell, and it is in period 2.
