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