Chapter 1: The Atom Flashcards
- What are molecules?
Molecules are a collection of atoms with a definite structure held together by covalent bonds. They are ALWAYS electrically neutral.
- What are atoms?
Atoms are a chemically discrete species. They have a central positively charged nucleus (protons(+1) and neutrons (neutral)). They have a nucleus surrounded by negatively charged electrons. They are ALWAYS electrically neutral (# electrons = # protons).
- What are ions?
Ions are a chemical species that have either a positive or negative electric charge.
- What are cations and anions?
Cation -> ions with a positive charge (removing an electron).
Anion -> ions with a negative charge (adding an electron).
- What are elements?
Elements are a collection of a single type of atom only. There are currently 118 different elements. Elements are arranged in the periodic table.
- What are compounds?
Compounds are substances containing 2 or more elements in definite and unchanging proportion.
- What is the Law of Conservation of Mass?
No detectable gain or loss of mass occurs in chemical reactions, i.e., mass is neither created or destroyed in chemical reactions.
- What is the Law of Definite Proportions?
In a given chemical compound, the elements are always combined in the same proportions by mass.
- What is Dalton’s Atomic Theory?
- Matter consists of tiny particles called atoms.
- Atoms are indestructible. In chemical reactions, the atoms rearrange but they do not themselves break apart.
- In any sample of a pure element, all elements are identical in mass and other properties.
- The atoms of different elements differ in mass and other properties.
- When atoms of different elements combine to form a given compound, the constituent atoms in the compound are always present in the same fixed ratio.
- What is the Law of Multiple Proportions?
Whenever 2 elements form more than 1 compound, the different masses of 1 element that combine with the same mass of the other element are in the ration of small whole numbers.
- What is the structure of the atom?
Atoms are comprised of a nucleus and surrounding electron(s).
- the nucleus occupies less than 0.1% of the total atomic volume.
- the nucleus is comprised of protons and neutrons.
- What does A mean?
X
Z
- X is the chemical symbol for any element.
- Z is the atomic number -> the number of protons in the nucleus.
- A is the mass number -> the number of protons plus the number of neutrons in the nucleus.
In a neutral atom the atomic number Z is also equal to the number of electrons.
- What are isotopes?
Isotopes are atoms of an element with the same number of protons but different numbers of neutrons.
- The periodic table organisation . . .
- elements may be ordered on the basis of increasing atomic number
- the periodic table is organised into:
- horizontal rows called periods
- vertical columns called groups
- What is meant by ‘electrons in atoms’?
Many of the chemical properties of an atom and it’s chemical reactivity are determined by the electrons.
- electrons occupy regions of space called orbitals
- each orbital has a characteristic electron distribution and energy
- When does an electronic transition occur?
It occurs when an atom absorbs a specific amount of energy and an electron is promoted to a higher orbital to form an excited state.
- What is a fundamental principle of quantum mechanics called quantisation?
That orbitals have definite energies.
- Electrons have . . .
- A single negative charge
- An intrinsic property called spin
- Spin can have only 2 value (spin up & spin down)
- Each orbital within an atom can contain a maximum of 2 electrons (1 spin up & 1 spin down)
- Covalent chemical bonds usually . . .
- consists of 1, 2 or 3 pairs of electrons shared between atoms
- Redox reactions involve . . .
- transfer of 1 or more electrons between chemical species
