Textbook Ch.2: Atoms, Molecules, and Ions Flashcards
What are the three parts of Dalton’s atomic theory?
- An element is composed of tiny particles called atoms. All atoms of a given element show the same chemical properties. Atoms of different elements show different properties
- In an ordinary chemical reaction, atoms move from one substance to another, but no atom of any element disappears or is changed into an
atom of another element - Compounds are formed when atoms of two or more elements combine. In a given compound, the relative numbers of atoms of each kind are definite and constant. In general, these relative numbers can be expressed as integers or simple fractions
Atom
the smallest particle of an element that can enter into a chemical reaction
Electrons
negatively charged particles that are common to all atoms, and carry a unit negative charge (-1), and have a very small mass, roughly 1/2000 that of the lightest atom
Protons
has a mass nearly equal to that of an ordinary hydrogen atom. The proton carries a unit positive charge (+1), equal in
magnitude to that of the electron (-1)
Neutrons
uncharged particles with a mass slightly greater than that of a proton
Law of conservation of mass
there is no detectable change in mass in an ordinary chemical reaction. If atoms are conserved in a reaction, the atomic mass will also be conserved
Law of constant composition
a compound always contains the same elements in the same proportions by mass. If the atom ratio of the elements in a compound is fixed, their proportions by mass must also be fixed
Law of multiple proportions
Applies in situations in which two elements form more than one compound
The law states that in these compounds, the masses of one element that combine with a fixed mass of the second element are in a ratio of small whole numbers
Atomic number
- All the atoms of a particular element have the same number of protons in the nucleus
- Given the symbol Z
Z = number of protons
In a neutral atom…
the number of protons = number of electrons
Mass number
- Found by adding up the number of protons and neutrons in the nucleus
- Given the symbol A
A = number of protons + number of neutrons
All atoms of a given element have the same _____, however, they can differ from one another in _____
all atoms of a given element have the same atomic number (Z), but they differ from one another in mass number (A)
Isotopes
atoms that contain the same number of protons but a different number of neutrons
Nuclear symbol
A symbol that shows the composition of a nucleus
- The atomic number (Z) appears as a subscript on the lower left of the symbol of the element
- The mass number (A) is written as a superscript in the the upper left
Radioactivity
when unstable isotopes decompose (decay)
Transmutation of elements
- The result of radioactivity
- The atomic number of the product nucleus differs from that of the reactant
- Can be beta particles identical in their properties to electrons
- Can be alpha particles, which are The particles Z=2, A=4 carrying a +2 charge
- Can be gamma rays, which consist of high-energy radiation
Periodic table
an arrangement of elements, in order of increasing atomic number, in horizontal rows of such a length that elements with similar chemical properties fall directly beneath one another in vertical groups
Periods
the horizontal rows in the periodic table
Groups
the vertical columns in the periodic table
Main-group elements
elements falling in Groups 1,2,13,14,15,16,17, and 18
Transition metals
elements falling in Groups 3-12
Post-transition metals
the metals in groups 13, 14, and 15
Alkali metals
a special name for the elements in group 1
- Lithium (Li), sodium (Na), and potassium (K) in this group all react vigorously with water to produce hydrogen gas
Alkaline earth metals
a special name for the elements in group 2
Halogens
a special name for the elements in group 17
Noble gases
a special name for the unreactive gases in group 18
- Helium (He), neon (Ne), and argon (Ar) do not react with any other substance
A diagonal line or stairway that starts to the left of boron in the periodic table separates ____ from ____
separates metals from nonmetals
Metals
elements with high electrical conductivities
Nonmetals
elements with low electrical conductivities
Metalloids
- Elements that are difficult to classify exclusively as metals or nonmetals
- They have properties between those of elements in the two classes
- Their electrical conductivities are intermediate between those of metals and nonmetals
- Boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te)
Ions
formed when an atom loses or gains electrons
Cations
positively charged ions
Anions
negatively charged ions
What happens to the subatomic particles of an atom when an ion is formed?
- The number of protons in the nucleus is unchanged
- The number of electrons increases or decreases
Monatomic ions
ions derived from a single atom by the loss or gain of electrons
Polyatomic ions
ions containing more than one atom
- the atoms are held together by covalent bonds in polyatomic ions
- you can think of polyatomic ions as a “charged molecule”
Ionic compounds
Compounds that contain both cations and anions in order to be electrically neutral
- Held together by STRONG electrical forces between oppositely charged ions referred to as ionic bonds
What are some properties of ionic compounds?
- Solids at room temperature
- Have relatively high melting points
- To melt an ionic compound requires that oppositely charged ions be separated from one another, thereby breaking ionic
bonds
Strong electrolyte
made when an ionic solid dissolves in water and therefore causing the ions to separate and the solution to conduct an electric current
Non-electrolytes
made when a molecular solid dissolves in water and does not conduct electricity
What does the principle of electrical neutrality require?
the total positive charge of the cations in the formula must be equal to the total negative charge of the anions
How can the charges of ions formed by atoms of the main-group elements be predicted?
atoms that are close to a noble gas (Group 18) in the periodic table form ions that contain the same number of electrons as the neighboring noble-gas atom
How are monatomic cations of main-group elements named?
take the name of the metal from which they are derived
Na+ sodium
K+ potassium
How are monatomic cations of transition and post-transition elements named?
with a roman numeral representing the charge because they can have multiple charges
Fe2+ iron (II)
Fe3+ iron (III)
How are monatomic anions named?
by adding the suffix -ide to the stem name of the nonmetal from which they are derived
Oxoanion
certain non-metals in Groups 15-17 of the periodic table form more than one polyatomic ion containing oxygen
How is the polyatomic ion named when a nonmetal forms two oxoanions?
- the suffix -ate is used for the anion with the largest number of oxygen atoms
- the suffix -ide is used for the anion containing fewer oxygen atoms
How is the polyatomic ion named when a nonmetal forms more than two oxoanions?
- The prefix per- is used meaning the largest number of oxygen atoms
- The prefix hypo- is used meaning the fewest oxygen atoms
What are the two words in an ionic compound?
- The first word names the cation
- The second word names the anion
Binary molecular compounds
when two nonmetals combine with each other
Describe the systematic way of naming a binary molecular compound.
- The first word gives the name of the element that appears first in the formula
- A Greek prefix is used to show the number of atoms of that element in the formula
- The second word consists of the appropriate Greek prefix designating the number of atoms in the second element
Acids
when a few binary molecular compounds containing H atoms ionize in water to form H⁺ ions
Oxoacids
acids that contain oxygen in addition to hydrogen
How are the prefixes replaced when dealing with oxoacids?
- -ate is replaced by -ic
- - ite is replaced by -ous
