Atomic theory Flashcards
What is an atom?
An atom is the smallest particle of an element, and the smallest unit of matter
What is a molecule?
A molecule is two or more atoms whose bonds bind together making the smallest unit in a compound (Oxygen molecule = 2 atoms of oxygen)
What is an element?
An element consists of one type of atom, each atom contains the same number of protons (Hydrogen)
What is a compound?
A compound consists of 2 more elements that are chemically bonded (held together by covalent or ionic bonds) in a fixed ratio, e.g. a water molecule (H2O), magnesium oxide (MgO)
What is a mixture?
A mixture is the physical combination of 2 or more substances in which the identities of the individual substances are retained, e.g., salt water (NaCl + H2O)
What is matter?
Matter is anything that has mass and volume
.
The
- Electrons travel around the nucleus in circular orbits
Structure of atom: Electron
Location: Electron cloud
Charge: -1
Relative mass: 1/1800
Structure of atom: Proton
Location: Nucleus
Charge: +1
Relative mass: 1
Structure of atom: Neutron
Location: Nucleus
Charge: 0
Relative mass: 1
What does an electron cloud do?
The negatively charged electron cloud gives atoms their size and mass
Describe the nucleus
The nucleus is 10,000-100,000 times smaller than the size of an atom but contributes to 99.97% of the mass - nuclei are very dense
What keeps atoms bound together?
Electrostatic attraction b/w electrons and protons keep the atom bound together
What is the atomic number?
The atomic number is the number of protons in the nucleus and is at the bottom of the chemical symbol
What is the mass number?
The mass number is the total number of protons and neutrons in nucleus, written at the top of the chemical symbol
How can you find the number of electrons?
The number of protons = number of electrons
How can you find the number of neutrons w the atomic number?
The atomic mass = the number of protons + neutrons, so take away the atomic mass from the atomic number which will give you the number of neutrons
What is electron configuration?
Shows the arrangement of electrons in an atom, where the number of electrons in each is separated by a comma
What is an ion?
A charged particle. Occurs as electrons may be gained or lost from the valence shell, when the number of protons and electrons are no longer equal, it produces a charged particle
What are anions?
Negatively charged ions, as electron is gained and outnumbers the number of protons
What are cations?
Positively charged, as electron is lost and protons outnumber electrons
Why do atoms lose/gain electrons?
Atoms tend to lose/gain electrons to achieve a full valence shell, giving it a similar configuration to the nearest noble gas
Which type of atoms become cations?
Metals tend to lose electrons, such as Mg
Which type of atoms become anions?
Non-metals tend to gain electrons such as Cl
How are the names of anions changed?
Anions are changed to end in -ide, for example chlorine turns to chloride, and oxygen turns to oxide
What is relative molecular mass?
(Mr) is the mass of a molecule of a substance relative to the mass of a carbon-12 atom. It is equal to the sum of the relative atomic masses of the atoms in the molecule
How can you calculate the relative molecular mass?
1) identify elements that make up the element
2) identify the no. of atoms that make up the element
3) add the relative mass of atoms that make up the element
