Chapter 2 Flashcards
What is an atom?
The smallest identifiable unit of an element.
Law of conservation of mass states…
…In a chemical reaction, matter is neither created nor destroyed.
Law of definite proportions states…
…that all samples of a given compound, regardless of their source or how they were prepared have the same proportions of their constituent elements.
Atomic theory
Is the theory that each element is composed of tiny indestructible particles called atoms, that all atoms of a given element have the same mass and other properties, and that atoms combine in simple, whole-numer ratios to form compounds.
Atomic Number (Z)
Number of protons in the nucleus of an atom; it describes the element
Mass Number (A)
The sum of protons and neutrons.
Isotopes
Atoms of the same element with different number of neutrons.
Radioacitivy
Is the spontaneous emission of energy by some atoms; there are three types: alpha, beta, and gamma
Alpha particles
+2 charge and large mass
Beta particles
-1 charge and small mass
Gamma particles
No charge, no mass
During chemical changes, atoms can…
…lose or gain electrons, becoming charged particles called ions.
Ions can occur in nature
True. Lithium and Fluorine are some of the examples.
Positively charged ions
Are called cations (Li+)
Negatively charged ions
Are called anions (F-)
Ions behavior similarly to their corresponding atoms
False.
Elements with similar properties…
…fall in the same columns (or groups)
Metal elements…
…Lay on the left side of the table, tend to be good conductors of electricity, have malleability, good ductility, are often shiny, and tend to lose electrons.
Non-metal elements…
…Lay on the upper right side (and hydrogen). These have varied properties; some are solids, other liquids, other gases, but they are mainly poor conductors of heat and electricity, and they all tend to gain electrons.
Metalloid elements…
…Lay on the diagonal line between non-metal and metal elements. Many of them are also classified as semiconductors.
Periodic table can also de divided into…
…Main-group elements (1A, 2A, 3A-8A) and transition elements (3B-2B)
8A elements
Noble gases
1A elements
Alkali metals; lose one electron, form 1+ ions
2A elements
Alkaline earth metals; tend to lose two electrons and form 2+ ions
7A
Halogens
Mass of an electron
9.10x10-29
Charge of an electron
-1.60x10-19C
1 amu
1.60x10 raised to -19
Molecular formula…
…provides the type and number of atoms in a given molecule
Empirical formula…
…gives the relative number of each type of atom in a compound. It is a starting point for a molecular formula
When going from molecular to empirical…
…look for a common factor.
Structural formula
Provides structure but nothing else; good for paper
Perspective
Attempts to illustrate a three dimensional state on a two dimensional state. It uses a wedge to represent an atom in the front; straight lines represent what is on the plane, and dashes represent what is behind.
Ball and stick
Shows a relative size of the molecules
Space-filling
Fills up the space between the atoms
Polyatomic atoms
They are joined together as a molecule, but with a net charge on the overall structure.
Atomic molecules
Exist in nature with single atoms as their basic unit
Molecular elements
Normally do not exist as single atoms, but within a combination of two or more atoms bonded together. Most of them exist as polyatomic molecules.
Molecular compounds
Made out of two or more covalently bound nonmetals
Ionic compounds
Ions attracted to each other due to electrostatic forces. When it’s formed, an electron is lost by an element and gained by other.
In a ionic compound…
…electrons are transferred. Usually the result of combinations between metals and nonmetals.
In a molecular compound…
Electrons are shared (which is called covalent bonding)
Arrangement of ions in a compound…
Three dimensional lattice.
Why do covalent bonds have a lower potential energy?
Because the shared electrons interact with both nuclei.
