Do Now: First fill in the table below. Which one of these particles is NOT counted in the mass number?0electroncloud Electron 10 In nucleus Neutron 1+1 In nucleus Proton MASS (amu) RELATIVE CHARGE LOCATION (in the atom) SUBATOMIC PARTICLE

Do Now: First fill in the table below. Which one of these particles is NOT counted in the mass number?0electroncloud Electron 10 In nucleus Neutron 1+1 In nucleus Proton MASS (amu) RELATIVE CHARGE LOCATION (in the atom) SUBATOMIC PARTICLE

3 x 2 = 6 H atoms Interpretation of a Chemical Formulas 1 molecule of sulfuric acid H 2 SO 4 Two atoms of hydrogen One atom of sulfur of sulfur Four atoms of oxygen of oxygen H H O S O O O How many hydrogen atoms are in three molecules of sulfuric acid?

3 x 2 = 6 H atoms Interpretation of a Chemical Formulas 1 molecule of sulfuric acid H 2 SO 4 Two atoms of hydrogen One atom of sulfur of sulfur Four atoms of oxygen of oxygen H H O S O O O How many hydrogen atoms are in three molecules of sulfuric acid?

Models of the Atom Dalton’s model (1803) Thomson’s plum-pudding model (1897) Rutherford’s model (1909) Bohr’s model (1913) Charge-cloud model (present) Dorin, Demmin, Gabel, Chemistry The Study of Matter, 3 rd Edition, 1990, page 125 Democritus’s model (400 B.C.) John Dalton pictures atoms as tiny, indestructible particles, with no internal structure J.J. Thomson, a British scientist, discovers the electron, leading to his "plum-pudding" model. He pictures electrons embedded in a sphere of positive electric charge Hantaro Nagaoka, a Japanese physicist, suggests that an atom has a central nucleus. Electrons move in orbits like the rings around Saturn New Zealander Ernest Rutherford states that an atom has a dense, positively charged nucleus. Electrons move randomly in the space around the nucleus In Niels Bohr's model, the electrons move in spherical orbits at fixed distances from the nucleus Frenchman Louis de Broglie proposes that moving particles like electrons have some properties of waves. Within a few years evidence is collected to support his idea Erwin Schrodinger develops mathematical equations to describe the motion of electrons in atoms. His work leads to the electron cloud model James Chadwick, a British physicist, confirms the existence of neutrons, which have no charge. Atomic nuclei contain neutrons and positively charged protons e e e e ee e e e e

Isotopes =  atoms of the same element with different mass numbers (because they have different #’s of neutrons) Mass # Atomic # Atomic symbol: Atomic symbol: Hyphen notation: boron-11 Hyphen notation: boron-11 (protons + neutrons) (only protons)

= proton = neutron (no electrons shown) # of # of atomic mass Protons neutronsnumbernumber symbol A B

= proton = neutron (no electrons shown) # of # of atomic mass Protons neutronsnumbernumber symbol A B B5B B5B boron-10 What’s the hyphen notation for A? boron-10

= proton = neutron (no electrons shown) # of # of atomic mass Protons neutronsnumbernumber symbol A B B5B B5B boron-10 What’s the hyphen notation for A? boron-10

Let’s compare carbon-12 & carbon Nucleus Electrons Carbon-12 Neutrons 6 Protons 6 Electrons Carbon-14 Neutrons ? Protons 6 Electrons6 Nucleus Electrons 8 n How many neutrons are in carbon-14? 8 n

Let’s compare carbon-12 & carbon Nucleus Electrons Carbon-12 Neutrons 6 Protons 6 Electrons Carbon-14 Neutrons 8 Protons 6 Electrons6 Nucleus Electrons 8 n How many neutrons are in carbon-14? 8 n

Atomic # Mass # Carbon-12 Atomic # Mass # Carbon-14

20 n Isotopes – review How many neutrons in chlorine-37 ? 20 n  Chlorine-37  atomic #: 17  mass #: 37  # of protons: 17  # of electrons: 17  # of neutrons: ??? Courtesy Christy Johannesson

20 n Isotopes – review How many neutrons in chlorine-37 ? 20 n  Chlorine-37  atomic #: 17  mass #: 37  # of protons: 17  # of electrons: 17  # of neutrons: 20 Courtesy Christy Johannesson

IONS electrons  Ions are atoms that have lost or gained electrons.  An atom that loses an electron becomes a positive ion (CATION)  An atom that gains an electron becomes a negative ion (ANION)

REVIEW OF SUB/SUPER-SCRIPTS E charge formulaatomic # mass # HOMEWORK –  #’s 42,65-67,69 & review any old homework that was tough to get ready for tomorrow’s parking lot review!

EXAMPLES OF IONS 1. A magnesium atom loses two e - and becomes which cation? Mg 2+  12 protons  12 neutrons (usually)  12 electrons

EXAMPLES OF IONS A magnesium atom loses two e - and becomes which cation? Mg → Mg e -  12 protons  12 neutrons (usually)  10 electrons

EXAMPLES OF IONS A chlorine atom gains one e - and becomes which anion? Cl 1-  17 protons  18 neutrons (usually)  17 electrons

EXAMPLES OF IONS A chlorine atom gains one e - and becomes which anion?  17 protons  18 neutrons (usually)  18 electrons Cl + e - → Cl 1-

EXAMPLES OF IONS If magnesium and chloride bond together, what’s the formula of the compound they form? MgCl 2 magnesium chloride… more on this next chapter

EXAMPLES OF IONS If magnesium and chloride bond together, what’s the formula of the compound they form? MgCl 2 magnesium chloride… more on this in chapter 5