2.1- The Nature of Matter Flashcards
What is an Atom?
Subatomic particles that make up an atom:
the basic unit of matter
protons, neutrons, electrons
What is the nucleus?
the center of an atom that contains positivley charged protons, and neutrons with no charge
What are electrons?
negativley charged particles with almost no mass, and are in constant motion in the space surrounding the nucleus
Atoms have an ———– so they are neutral
equal number of electrons and protons
What is an element?
a pure substance that is entirely one type of atom
How are the elements orgainzed?
By atomic number (the number of protons each atom has)
What are isotopes
atoms of the same element that have a differnet number of neutrons
What is atomic mass number?
the total number of protons and neutrons in the nucleus
Radioactive isotopes are both:
extremly dangerous but helpful
What is a compound?
a substance formed by the chemical combination of 2 or more elements in definite proportions
A chemical formula:
shows the compostion of compounds
Ex: NaCl (table salt)
Physical and chemical properties of compounds are:
Example:
very differnet from the elements that form them
Chlorine is very reactive but forms sodium chloride which essentail for
Chemical Bonds:
hold atoms in compounds together
bond formation involves valence electrons (electrons in the outer shell)
What is an ionic bond?
When 1 or more electrons are transferred from one atom to another, resulting in ions that attract to each other becuase of their opposite charges
What is an ion?
when an atom loses or gains electrons and becomes positively or negatively charged
What is a covalent bond?
when atoms ‘share’ electrons; the electrons travel around both nuclei
What are single, double, and triple covalent bonds?
Single: 2 shared electrons
Double: 4 shared electrons
Triple: 6 shared electrons
What is a molecule?
the smallest unit of most compounds; formed when atoms are jioned by covalent bonds
What are van der Waals forces?
when molecules are close together and a slight attration develops between the oppositely charged regions of nearby molecules
Ex: geckos
Atoms are:
the building blocks of matter
What is chemistry?
the study of matter’s composition and properties
Matter:
anything that has mass and takes up space
Who propsed the idea that all matter is made up of tiny particles?
Greek Philosophers Leucippus and Democratis
When did scientists begin to collect evidence to support the existence of atoms?
1800s
Dimitri Mendeleev:
late 1800s, Russian
orgainized the elements based on increasing atomic mass
Henrey Mosely:
led movemnet to organize the elements by atomic number, not mass
What is the purpose of neutrons?
to prevent protons from repeling each other
(same charges repell, think of magnet)
Electrons determine:
the chemical properties of atoms
Electron cloud, properties determined by electrons in the outer orbit
Example of electron property:
hydrogen is very reactive becuase it has only 1 electron and wants 2 to become for stable
What element does not have a neutron
hydrogen
How do you determine the number of neutrons of an element?
subtract the number of protons from the atomic mass
Atomic mass is the average of the isotopes too
When you increase the number of neutrons in an atoms…
the atoms begins to degrade making it radioactive (affects stability)
What is Carbon-14 used for?
to determine the age of fossils and to locate and treat some cancers
found in all living things
What is radioactive iodine used for?
to treat thyroid cancer
What is radioactive barium used for?
to detect abnormalities in the gastrointinal tract
(MRI replaced this)
How many compounds are there?
millions
Wetlands produce how much of global methane?
76%
Liquids and gasses are formed by:
covalent bonds
Examples: water, methane, hydrochloric acid
Solids are formed by:
ionic bonds
