Chapter 2 Flashcards
Matter
Is anything that takes up space and has mass.
Is made up of elements.
Element
Is a substance that cannot be broken down to other substances by chemical reactions.
Compound
Is a substance consisting of two or more different elements combined in a fixed ratio.
A compound has characteristics different from those of its elements, meaning it often has emergent properties.
Mass
The amount of matter in an object.
Essential Elements
An organism needs essential elements to live a healthy life and reproduce. They are similar among organisms, but there is some variation.
For example, humans need 25 elements, but plants need only 17.
Four elements that make up 96% of living matter
Oxygen (O)
Carbon (C)
Hydrogen (H)
Nitrogen (N)
Trace elements
Are required by an organism in only minute quantities.
Atom
Is the smallest unit of matter that still retains the properties of an element.
Subatomic particles
Compose an atom. There are more than a hundred types of subatomic particles, however these are important for now: Neutrons, protons, electrons.
Proton
Has one unit of positive charge
Electron
Has one unit of negative charge.
Neutron
Is electrically neutral.
Atomic Nucleus
The dense core at the center of an atom. Protons and neutrons are packed together tightly in the atomic nucleus. Electrons are rapidly moving around the nucleus, and it is the attraction between opposite charges that keeps the electrons in the vicinity of the nucleus.
Dalton
Unit of measurement used for subatomic particles, atoms, and molecules.
Equal to about 1.7 x 10^-24 gram.
Same as the atomic mass unit (amu)
Mass of neutrons and protons
Close to 1 dalton.
Mass of electron
About 1/2,000 of a neutron or proton.
Atomic number
Number of protons, unique to each element.
Mass number
The sum of protons plus neutrons in the nucleus of an atom.
Atomic mass
The total mass of an atom
Isotopes
Atoms with more neutrons than other atoms of the same element.
Decay
A process where the nucleus has a tendency to lose subatomic particles.
Radioactive isotope
An isotope in which the nucleus decays spontaneously, giving off particles and energy. When the radioactive decay leads to a change in the number of protons, it transforms the atom to an atom of a different element.
Half-life
The time it takes for 50% of the parent isotope to decay.
Energy
The capacity to cause change, for instance, by doing work.