Chapter 2 atoms & elements Flashcards
1 Law of conservation of mass:
A mass stating that matter is neither created nor destroyed. * In other words, when a chemical reaction occurs, the total mass of the substances involved in the reaction does not change.
2 Law of definite Portions
When two elements (call them A and B) form two different compounds, the masses of element B that combine with 1g of element A can be expressed as a ratio of small whole numbers.
3 Cathode
The electrode in an electrochemical cell at which reduction occurs; electrons flow toward the cathode.
4 Cathode Rays
A stream of electrons produced when a high voltage is applied between two electrodes within a partially elevated tube.
5 Electrical Charge
A fundamental property of certain particles that can cause them to experience a force in the presence of electric fields.
6 Electron
Negatively charged low-mass particles found outside the nucleus of all atoms that occupies most of the atoms’s volume, but contributes none of its mass.
7 Radio Activity
The emission of subatomic particles or high energy electromagnetic radiation by unstable nuclei of certain atoms.
8 Nuclear Theory
The theory that out of the atom’s mass and all of its positive charged are contained in a small , dense nucleus.
9 The Nuclear Theory with, Three basic parts
- Most of the atoms mass and all of its positive charges are contained in a small core called the nucleus.
- Most of the volume of the atom is empty space, throughout which tiny negatively charged electrons are dispersed.
- There are many negatively charged electrons found outside the nucleus as there are positively charged particles (called protons) within the nucleus, so the atom is electrically neutral.
10 Nucleus
Thievery small, dense core of the atom that contains most of the atoms and all of its positive charge; composed of protons and neutrons
11 Protons
A positively charged subatomic particle found in the nucleus of an atom.
12 Electron
A negatively charged, low-mass particle found outside the nucleus of all atoms that occupies most of the atom’s volume but contributes almost none of its mass.
13 Neutron
An electrically neutral subatomic particle found in the nucleus of an atom, with a mass almost equal to that of a proton.
14 Atomic Mass Unit (AMU)
A unit used to express the masses of atoms and subatomic particles, defined as 1/12 the mass of a carbon atom containing 6 protons and 6 neutrons.
15 Atomic Number
The number of protons in an atom; the atomic number defines the element.
