General Chemistry placement test Study Guide 2024 Solved 100%

Atomic Number - The number of protons in the nucleus of an atom. The atomic number of an element never changes, meaning that the number of protons in the nucleus of every atom in an element is always the same. Hydrogen = 1, Carbon = 6, Oxygen = 8 (located on top of element of periodic table) Mass Number - # of neurons + # of protons = mass number (located on bottom of periodic table) Isotopes - Let's say an atom is missing a neutron or has an extra neutron. That type of atom is called an isotope. An atom is still the same element if it is missing an electron. Example: (carbon-14) Distribution B/W subatomic particles in an Atom - A typical atom consists of three subatomic particles: Protons, Neutrons, and Electrons. - Nucleons include protons and neutrons. All the positive charge of an atom is contained in the nucleus, and originates from the protons. Neutrons are neutrally-charged. Electrons, which are negatively-charged, are located outside of the nucleus. Roles of subatomic particles: Protons, Neutrons, & Electrons - Particle Mass: Protons & Neutrons have about same mass. Electrons have much less mass than protons and neutrons. Particle Charge: Protons have a positive charge (+) - Neutrons have no charge (0) - Net charge of the nucleus is positive and equal to the number of protons. - Electrons have a negative charge (-) - Atoms are neutrally charged when the number of electrons is the same as the number of protons. Particle identity: The number of protons determines the identity of an atom (an element). - Atoms of the same element have the same number of protons, the number of neutrons may vary. - An atom of a given element may lose or gain electrons yet it still remains the same element. Periodic Table: (Metals) - - They are solid (with the exception of mercury, Hg, a liquid). - They are shiny, good conductors of electricity and heat. - They are ductile (they can be drawn into thin wires). - They are malleable (they can be easily hammered into very thin sheets). Periodic Table: (Non-metals) - The nonmetals are brittle, not malleable or ductile, poor conductors of both heat and electricity, and tend to gain electrons in chemical reactions. Some nonmetals are liquids. (hydrogen is considered a nonmetal) Periodic Table: (Semi-metals/Mettaloids) - Atoms - Smallest pieces of matter; made up of protons (+) and electrons (-). Molecules - Are Atoms grouped together (compound). Does NOT carry electrical charge like ions. All compounds are molecules; not all molecules are compounds. Example: (H2O, N2, O3) Elements - A substance made of Atoms containing the same number of protons in their atomic nuclei. Example: (Iron, Copper, Hydrogen, & Oxygen). Compounds - A substance made up of two or more elements joined by chemical bonds into a molecule. The elements are combined in a definite ratio. Example: (H2O, NaCl) Polyatomic Ions - A charged chemical species composed of more than one element. Example: (Hydroxide ion; 1O + 1H = OH-) Diatomic Ions - Composed of multiple molecules of the same element. 7 diatomic elements in total. Consist of gases and Halogens. Examples: Gases = (Hydrogen H2, Nitrogen N2, Oxygen O2) Halogens = (Flourine F2, Chlorine Cl2, Iodine I2, Bromine Br2) Homonuclear molecules - Molecules composed of only 1 element. Consists of Diatomic molecules Heteronuclear molecules - Molecules composed of more than one element. Examples: (Carbon Monoxide, Hydrogen Floride) Chemical Change - Any change that results in the formation of new chemical substances. At the molecular level, chemical change involves making or breaking of bonds between atoms, resulting in the formation of a new substance. Example: (iron rusting, eggs cooking) Physical Change - A change that rearranges molecules but doesn't affect their internal structures, no new substance in formed. Examples: (Whipping eggs, Boiling water, dicing potatoes) Gas - - Particles in gas: are well separated with no regular arrangement & also vibrate and move freely at high speeds. - Assumes the shape and volume of its container: particles can move past one another. - Compressible: lots of free space between particles. - Flows easily: particles can move past one another. Liquid - - Particles in a liquid: are close together with no regular arrangement. The particles also vibrate, move about, and slide past each other. - Assumes the shape of the part of the container which it occupies: particles can move/slide past one another. - Not easily Compressible: (little free spaces b/w particles. - Flows easily Solid - - Particles in a solid are tightly packed, usually in a regular pattern. Particles also jiggle, but do not move from place to place. - Retains a fixed volume & shape. - Not easily compressible (little space to move) - Does NOT flow easily Ionic Bond - A bond composed of a metal; cation (+) and a nonmetal; anion (-). Covalent Bond - A bond composed of two nonmetal elements (-). (sharing elections) Metallic Bond - A bond composed of two metal elements. (sharing elections) Nonpolar Bond - Has a uniformed distribution of electron charge. (CO2) - The difference is usually small of none. Polar Bond - Unsymmetric electron cloud distribution (HCl) - The difference is usually large. two nonmetal atoms combined form a covalent compound called a - molecule H2,O2,F2 - diatomic molecules Anything that has mass and takes up space - Matter A substance that cannot be broken down into simpler substances - Element