[NOTES] Chapter 2: The Components of Matter Flashcards
Element
The simplest type of matter with unique physical and chemical properties
Atom
The smallest unit of an element that retains its chemical nature
Compound
Consists of two or more different elements that are bonded chemically
- elements are present in fixed parts by mass (fixed mass ratio) because each unit of a compound consists of a fixed number of atoms of each element
- a compound’s properties are different from the properties of its elements
Mixture
Consists of two or more substances (elements and/or compounds that are physically intermingled, not chemically combined
Law of Mass Conservation
The total mass of substances does not change during a chemical reaction
- mass cannot be created nor destroyed
Law of Definite (or constant) Composition
No matter what its sourced, a particular compound is composed of the same elements in the same parts (fractions) by mass
Fraction by Mass (Mass Fraction)
The part of the compound’s mass that each element contributes
- mass fraction = (mass of element X in compound A) / mass of compound A
Percent by Mass (Mass percent, mass %)
The fraction by mass expressed as a percentage (multiplied by 100)
- mass percent = mass friction x 100
Postulates of the Atomic Theory
- All matter consists of atoms
- Atoms of one element cannot be converted into atoms of another element
- Atoms of an element are identical in mass and other properties and are different from atoms of any other element
- Compounds result from the chemical combination of a specific ratio of atoms of different elements
Mass Conservation
Atoms cannot be created or destroyed (P1) or converted into other types of atoms (P2), therefore, a chemical reaction cannot possibly result in a mass change because atoms are just combined differently
Definite Composition
A compound is a combination of a specific ratio of different atoms (P4), each of which has a particular mass (P3), thus, each element in a compound must constitute a fixed fraction of the total mass
Multiple Proportions
Atoms of an element have the same mass (P3) and are indivisible (P1). The masses of element B that combine with a fixed mass of element A must give a small, whole-number ratio because different numbers of B atoms combine with each A atom in different compounds
Cathode Rays
Originated at the negative electrode (cathode) and moved to the positive electrode (anode)
- ex. when the electric power source was turned on, a “ray” could be seen striking the phosphor-coated end of the tube, which emitted a glowing spot of light
Ernest Rutherford’s Conclusion
Alpha particles were being repelled by something small, dense, and positive; he found
- an atom is mostly space occupied by electrons
- the center contains a tiny region called the “nucleus”, that contains all the positive charge and essentially all the mass of the atom
Proton (p^+)
Positive charge in the nucleus, 1+
Neutron (n^0)
No charge, in the nucleus
- mass of proton or neutron is nearly 2000x the mass of an electron
Electron (e^-)
Negative charge, 1-
- an atom is neutral because the number of protons in the nucleus equals the number of electrons surrounding the nucleus
Atomic Number (Z)
Equals the number of protons in the nucleus of each of its atoms
- all atoms of an element have the same atomic number, and the atomic number of each element is different from that of any other element
Mass Number (AO
The total number of protons and neutrons in the nucleus of an atom
- each proton and each neutron contributes one unit to the mass number
Atomic (Element) Symbol
Element name based on its English, Latin, or Greek name
Isotopes
Atoms that have different numbers of neutrons and therefore different mass numbers
- most elements occur in nature in a particular isotopic composition, which specifies the proportional abundance of each of its isotopes
Atomic Mass Unit (amu)
A measurement relative to the mass of an atomic standard (carbon-12 atom), therefor the amu is 1/12 the mass of a carbon-12 atom
- the unit has, however, been changed to the dalton (Da)
Mass Spectrometry
A method for measuring the relative masses and abundances of atomic-scale particles very precisely
Periodic Table of the Elements
Based on Mendeleev’s version (but arranged by atomic number, not mass), is one of the great classifying schemes in science and an indispensable tool
- boxes are arranged into a grid of periods (horizontal rows) and groups (vertical columns)
Ionic Compounds
Transferring elections from atoms of one element to atoms of another to form
Covalent Compounds
Sharing electrons between atoms of different elements
Chemical Bonds
The forces that hold the atoms together in a compound
Ions
Charged particles that form when an atom (or small group of atoms) gains or loses one or more electrons
Binary Ionic Compound
Simplest type of ionic compound where one composed of ions of two elements, it is typically formed when a metal reacts with a nonmetal
Cation
A positively charged ion when a metal atom loses one or more electrons
Anion
Negatively charged ions, each nonmetal atom gains one or more of the electrons lost by the metal atom
Monatomic Ion
A cation or an anion derived from a single atom
Coulomb’s Law
The energy of attraction (or repulsion) between two particles is directly proportional to the product of the charges and inversely proportional to the distance between them
- energy <>< (charge 1 X charge 2)/distance
- Ions with higher charges (or repel) each other more strongly than do ions with lower charges
- Smaller ions attract (or repel) each other more strongly than do larger ions, because the charges are closer to each other
Covalent Bond
A pair of electrons mutually attracted by the two nuclei
Polyatomic Ions
Consists of two or more atoms bonded covalently and have a net positive or negative charge
Chemical Formula
Element symbols and numerical subscripts show the type and number of each atom in the smallest unit of the substance
Formula Unit
Contains the relative numbers of cations and anions in the compound
Oxoanions (Oxyanions)
Element, usually a nonmental, is bonded to one or more oxygen atoms
Hydrates
Ionic compounds that have a specific number of water molecules in each formula unit
Binary Covalent Compounds
Typically formed by the combination of two nonmetals
Molecular Mass/Weight
Of a molecule or formula unit of the compound as the sum of the atomic masses
- Molecular Mass = sum of atomic masses
Heterogeneous Mixture
Has one or more visible boundaries among the components
Homogeneous Mixture (or Solution)
Has no visible boundaries because the components are individual atoms, ions, or molecules
Filtration
Based on differences in particle size and is often used to separate a solid from a liquid, which flows through the tiny holes in filter paper as the solid is retained
Crystallization
Based on differences in solubility, refers to a substance that dissolves in a fixed volume of a solvent at a given temperature
Distillation
Separates components through differences in volatility, the tendency of a substance to become a gas
