Chapter 2- Basic Chemistry Flashcards
____________ elements are essential to life.
Twenty-five
Elements
- matter that cannot be broken down into other substances.
- 92 naturally occuring elements
- only 6 make up 98% body weight of organisms
- CHNOPS
__________ elements occur in smaller amounts.
Trace
Atoms
- smallest basic unit of matter
- protons and neutrons found in nucleus
- electrons orbit nucleus
atoms are composed of _____________ particles.
subatomic
Mass number equals _______ of protons and neutrons.
sum
Electrons orbit the nucleus of an atom in specific ____________ __________.
Electron shells
-# of electrons in outermost shell determines the chemical properties of an atom
Electrons are attracted to the nucleus, and thus ____________ is required to push electrons into higher orbits.
Energy
________ models show energy levels and electron shells.
Bohr
Shells are complete when they are _________ with electrons.
filled
Atoms with fewer than 8 electrons in the outer shell are said to be _________.
Reactive
Isotopes are alternate _________ forms of an element.
mass
Isotopes
- have the same number of protons and electrons
- different number of neutrons.
_______________ isotopes spontaneously decay and give off energy in the form of rays and subatomic particles.
Radioactive
-can be used as tracers and mutagens
atoms are held together by __________ ________.
Chemical bonds
what is a molecule?
-two or more atoms bonded together.
what is a compound?
-two or more different types of atoms bonded together
Ionic bonds are formed when electrons are _____________ from one atom to another
transferred
-each transfer causes a charge imbalance in each atom.
Oppositely charged ions are ___________ to one another, forming ionic bonds.
attracted
Covalent bonds are formed when two atoms _______ electrons so that each atom has a complete outer shell.
share
Covalent bonds are…
-stronger than ionic bonds.
Molecules have…
three dimensional shapes.
