Elements, Atoms, and Ions

The Language of Chemistry ELEMENTS –pure substances that cannot be decomposed by ordinary means to other substances. Sodium Bromine Aluminum COPY!!! DON’T SKETCH!!!

The Language of Chemistry The elements, their names, and symbols are given on the PERIODIC TABLEThe elements, their names, and symbols are given on the PERIODIC TABLE There are 118 of themThere are 118 of them READ ONLY!!!

The Periodic Table Dmitri Mendeleev ( ) “Father of the Periodic Table” READ ONLY!!!

Glenn Seaborg ( ) Discovered 8 new elements.Discovered 8 new elements. Only living person for whom an element was named.Only living person for whom an element was named. READ ONLY!!!

An atom consists of a nucleusnucleus –(of protons and neutrons) electrons in space about the nucleus.electrons in space about the nucleus. The Atom Nucleus Electron cloud COPY ALL!!! SKETCH!!!

Copper atoms on silica surface. An ATOM is the smallest particle of an element that has the chemical properties of the element.An ATOM is the smallest particle of an element that has the chemical properties of the element. Distance across = 1.8 nanometer (1.8 x m) COPY!!! DON’T SKETCH!!!

The red compound is composed of nickel (Ni) (silver) carbon (C) (black) hydrogen (H) (white) oxygen (O) (red) nitrogen (N) (blue) CHEMICAL COMPOUNDS occur when atoms combine, and can be un- combined to those atoms. COPY!!! DON’T SKETCH!!!

Compounds –composed of 2 or more elements in a fixed ratio –properties differ from those of individual elements –EX: table salt (NaCl) COPY!!! DON’T SKETCH!!!

A MOLECULE is the smallest unit of a compound that retains the chemical characteristics of the compound. Composition of molecules is given by a MOLECULAR FORMULA H2OH2OH2OH2O C 8 H 10 N 4 O 2 - caffeine COPY!!! DON’T SKETCH!!!

ELEMENTS THAT EXIST AS DIATOMIC MOLECULES Remember: Br HONClIF A trick for remembering: “Brother Honcliff” These elements only exist as PAIRS. Note that when they combine to make compounds, they are no longer elements so they are no longer in pairs! COPY ALL!!! DON’T SKETCH!!!

Dalton’s Atomic Theory John Dalton ( ) proposed an atomic theory While this theory was not completely correct, it revolutionized how chemists looked at matter and brought about chemistry as we know it today instead of alchemy Thus, it’s an important landmark in the history of science. READ ONLY!!!

Dalton’s Atomic Theory - Summary 1.matter is composed, indivisible particles (atoms) 2.all atoms of a particular element are identical 3.different elements have different atoms 4.atoms combine in certain whole-number ratios 5.In a chemical reaction, atoms are merely rearranged to form new compounds; they are not created, destroyed, or changed into atoms of any other elements. READ ONLY!!!

Problems with Dalton’s Atomic Theory? 1. matter is composed, indivisible particles Atoms Can Be Divided, but only in a nuclear reaction 2. all atoms of a particular element are identical Does Not Account for Isotopes (atoms of the same element but a different mass due to a different number of neutrons)! 3. different elements have different atoms YES! 4. atoms combine in certain whole-number ratios YES! Called the Law of Definite Proportions 5. In a chemical reaction, atoms are merely rearranged to form new compounds; they are not created, destroyed, or changed into atoms of any other elements. Yes, except for nuclear reactions that can change atoms of one element to a different element COPY ALL!!!

ATOM COMPOSITION protons and neutrons in the nucleus.protons and neutrons in the nucleus. the number of electrons is equal to the number of protons.the number of electrons is equal to the number of protons. electrons in space around the nucleus.electrons in space around the nucleus. Atoms are extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water! Atoms are extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water! The atom is mostly empty space COPY ALL!!!

ATOMIC COMPOSITION Protons (p + )Protons (p + ) –positive (+) electrical charge –mass = x g –relative mass = atomic mass units (amu) but we can round to 1 Electrons (e - )Electrons (e - ) – negative (-) electrical charge –relative mass = amu but we can round to 0 Neutrons (n o )Neutrons (n o ) – no (0) electrical charge –mass = amu but we can round to 1 COPY ALL!!!

Atomic Number, Z All atoms of the same element have the same number of protons in the nucleus, which we call “Z” 13 Al Atomic number Chemical symbol AVERAGE Atomic Mass COPY ALL!!!

Mass Number, A C atom with 6 protons and 6 neutrons is the mass standardC atom with 6 protons and 6 neutrons is the mass standard = 12 atomic mass units= 12 atomic mass units Mass Number (A) = # protons + # neutronsMass Number (A) = # protons + # neutrons NOT on the periodic table…(it is the AVERAGE atomic mass on the table)NOT on the periodic table…(it is the AVERAGE atomic mass on the table) A boron atom can have A = 5 p + 5 n = 10 amuA boron atom can have A = 5 p + 5 n = 10 amu Copy ALL!!! Sketch!!!

Atomic Symbols Show the name of the element, a hyphen, and the mass number in hyphen notation sodium-23 Show the mass number and atomic number in nuclear symbol form mass number 23 Na atomic number 11 Copy ALL!!!

Counting Protons, Neutrons, and Electrons Protons: Atomic Number (from periodic table) Electrons: –If it’s an atom, the protons and electrons must be the SAME so that it is has a net charge of zero (equal numbers of + and -) Neutrons: Mass Number minus the number of protons (mass number is protons and neutrons because the mass of electrons is negligible) Means we can ignore electrons’ weight because it’s SO TINY Copy ALL!!!