Unit 6 Flashcards
“Standard Model”
What our current understanding of subatomic particles is known as
Atom
building block of matter
Element
Material composed of only one kind of atom
How many elements are known?
- 90 occur naturally.
Every simple, complexing, living, or nonliving substance in the known universe is put together…
from a pantry containing less than 100 elements.
Atoms are so small that there are about…
10^23 atoms in a gram of water.
Atoms in body have been around since…
more than 4.6 billion years ago.
Brownian motion
perpetual jiggling of particles that are just large enough to be seen.
Brownian motion is evidence…
that atoms exist, as it results from the motion of neighboring atoms and molecules. They bump into the larger particles that we can see.
Molecule
Smallest particle of a substance consisting of two or more atoms that bond together by sharing electrons.
Molecules can be made up of…
atoms of the same element or of different elements.
Compound
Substance that is made of atoms of different elements combined in a fixed proportion.
Chemical formula
Tells the proportions of each kind of atom for a compound.
Compounds have properties different from those of…
the elements of which they are made.
Nucleus
Where almost all of an atom’s mass is packed into a dense central region.
Nucleons
Principal building blocks of the nucleus.
Neutrons
Nucleons in an electrically neutral state
Protons
Nucleons in an electrically charged state
Isotope
Atoms of the same element having different numbers of neutrons.
Deuterium
When proton is accompanied by a neutron
Tritium
When two neutrons are in a hydrogen nucleus.
Atomic number
The number of protons in the nucleus.
Ion
Atom with a net charge.
Shell model of atom
- electrons are pictured as orbiting in spherical shells around the nucleus.
- there are seven different shells, each has its own capacity for electrons
The arrangement of electrons in the shells around the atomic nucleus dictates…
the atom’s chemical properties.
Four phases of matter
Solid, liquid, gaseous, and plasma
Plasma
Consists of positive ions and free electrons. Phase exists only at high temperatures.
Crystals
Regular geometric shapes whose component particles are arranged in an orderly, repeating pattern.
The shape of a crystal mirrors the…
geometric arrangement of atoms within the crystal.
Density
Measure of how much matter occupies a given space.
density = mass/volume
The density of a material depends upon…
the masses of the individual atoms that make it up, and the spacing between those atoms.
Weight density
Amount of weight a body has per unit of volume.
weight density = weight/volume
Specific gravity
Standard measure of density. The ratio of mass (or weight) of a substance to mass (or weight) of an equal volume of water.
Elastic
Material that returns to its original shape after is has been stretched or compressed.