Elements Ions Isotopes

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Slide 1:

Elements, Atoms, and Ions Chemistry I: Chapter 2b Chemistry I Honors: Chapter 3 ICP: Chapter 17 SAVE PAPER AND INK!!! When you print out the notes on PowerPoint, print "Handouts" instead of "Slides" in the print setup. Also, turn off the backgrounds (Tools>Options>Print>UNcheck "Background Printing")!

The Language of Chemistry :

The Language of Chemistry CHEMICAL ELEMENTS - pure substances that cannot be decomposed by ordinary means to other substances. Sodium Bromine Aluminum

The Language of Chemistry :

The Language of Chemistry The elements, their names, and symbols are given on the PERIODIC TABLE How many elements are there?

The Periodic Table :

The Periodic Table Dmitri Mendeleev (1834 - 1907)

Glenn Seaborg(1912-1999 ) :

Glenn Seaborg(1912-1999 ) Discovered 8 new elements. Only living person for whom an element was named.

Slide 9:

An atom consists of a nucleus (of protons and neutrons) electrons in space about the nucleus. The Atom

Copper atoms on silica surface. :

Copper atoms on silica surface. An _____ is the smallest particle of an element that has the chemical properties of the element. Distance across = 1.8 nanometer (1.8 x 10-9 m)

Subatomic Particles :

Subatomic Particles Quarks component of protons & neutrons 6 types 3 quarks = 1 proton or 1 neutron

The red compound is composed of • nickel (Ni) (silver)• carbon (C) (black)• hydrogen (H) (white) • oxygen (O) (red)• nitrogen (N) (blue) :

The red compound is composed of • nickel (Ni) (silver)• carbon (C) (black)• hydrogen (H) (white) • oxygen (O) (red)• nitrogen (N) (blue) CHEMICAL COMPOUNDS are composed of atoms and so can be decomposed to those atoms.

Compounds :

Compounds composed of 2 or more elements in a fixed ratio properties differ from those of individual elements EX: table salt (NaCl)

A MOLECULE is the smallest unit of a compound that retains the chemical characteristics of the compound. :

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 H2O C8H10N4O2 - caffeine

ELEMENTS THAT EXIST AS DIATOMIC MOLECULES :

ELEMENTS THAT EXIST AS DIATOMIC MOLECULES Remember: BrINClHOF 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!

Dalton’s Atomic Theory :

Dalton’s Atomic Theory John Dalton (1766-1844) 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.

Dalton’s Atomic Theory - Summary :

Dalton’s Atomic Theory - Summary matter is composed, indivisible particles (atoms) all atoms of a particular element are identical different elements have different atoms atoms combine in certain whole-number ratios 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.

Problems with Dalton’s Atomic Theory? :

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

ATOM COMPOSITION :

ATOM COMPOSITION protons and neutrons in the nucleus. the number of electrons is equal to the number of protons. electrons in space around the nucleus. 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

ATOMIC COMPOSITION :

ATOMIC COMPOSITION Protons (p+) + electrical charge mass = 1.672623 x 10-24 g relative mass = 1.007 atomic mass units (amu) but we can round to 1 Electrons (e-) negative electrical charge relative mass = 0.0005 amu but we can round to 0 Neutrons (no) no electrical charge mass = 1.009 amu but we can round to 1

Atomic Number, Z :

Atomic Number, Z All atoms of the same element have the same number of protons in the nucleus, Z 13 Al 26.981

Mass Number, A :

Mass Number, A C atom with 6 protons and 6 neutrons is the mass standard = 12 atomic mass units Mass Number (A) = # protons + # neutrons 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 amu

Isotopes :

Isotopes Atoms of the same element (same Z) but different mass number (A). Boron-10 (10B) has 5 p and 5 n Boron-11 (11B) has 5 p and 6 n

Figure 3.10: Two isotopes of sodium. :

Figure 3.10: Two isotopes of sodium.

Isotopes & Their Uses :

Isotopes & Their Uses Bone scans with radioactive technetium-99.

Isotopes & Their Uses :

Isotopes & Their Uses The tritium content of ground water is used to discover the source of the water, for example, in municipal water or the source of the steam from a volcano.

Atomic Symbols :

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

Isotopes? :

Isotopes? Which of the following represent isotopes of the same element? Which element? 234 X 234 X 235 X 238 X 92 93 92 92

Counting Protons, Neutrons, and Electrons :

Counting Protons, Neutrons, and Electrons Protons: Atomic Number (from periodic table) Neutrons: Mass Number minus the number of protons (mass number is protons and neutrons because the mass of electrons is negligible) 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 -) If it does NOT have an equal number of electrons, it is not an atom, it is an ION. For each negative charge, add an extra electron. For each positive charge, subtract an electron (Don’t add a proton!!! That changes the element!)

Learning Check – Counting :

Learning Check – Counting Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12C 13C 14C 6 6 6 #p+ _______ _______ _______ #no _______ _______ _______ #e- _______ _______ _______

Answers :

Answers 12C 13C 14C 6 6 6 #p+ 6 6 6 #no 6 7 8 #e- 6 6 6

Learning Check :

Learning Check An atom has 14 protons and 20 neutrons. A. Its atomic number is 1) 14 2) 16 3) 34 B. Its mass number is 1) 14 2) 16 3) 34 C. The element is 1) Si 2) Ca 3) Se D. Another isotope of this element is 1) 34X 2) 34X 3) 36X 16 14 14

IONS :

IONS IONS are atoms or groups of atoms with a positive or negative charge. Taking away an electron from an atom gives a CATION with a positive charge Adding an electron to an atom gives an ANION with a negative charge. To tell the difference between an atom and an ion, look to see if there is a charge in the superscript! Examples: Na+ Ca+2 I- O-2 Na Ca I O

Forming Cations & Anions :

Forming Cations & Anions A CATION forms when an atom loses one or more electrons. An ANION forms when an atom gains one or more electrons Mg --> Mg2+ + 2 e- F + e- --> F-

PREDICTING ION CHARGES :

PREDICTING ION CHARGES In general metals (Mg) lose electrons ---> cations nonmetals (F) gain electrons ---> anions

Learning Check – Counting :

Learning Check – Counting State the number of protons, neutrons, and electrons in each of these ions. 39 K+ 16O -2 41Ca +2 19 8 20 #p+ ______ ______ _______ #no ______ ______ _______ #e- ______ ______ _______

One Last Learning Check :

One Last Learning Check Write the nuclear symbol form for the following atoms or ions: A. 8 p+, 8 n, 8 e- ___________ B. 17p+, 20n, 17e- ___________ C. 47p+, 60 n, 46 e- ___________

Charges on Common Ions :

Charges on Common Ions By losing or gaining e-, atom has same number of e-’s as nearest Group 8A atom.

AVERAGE ATOMIC MASS :

AVERAGE ATOMIC MASS Because of the existence of isotopes, the mass of a collection of atoms has an average value. Boron is 20% 10B and 80% 11B. That is, 11B is 80 percent abundant on earth. For boron atomic weight = 0.20 (10 amu) + 0.80 (11 amu) = 10.8 amu

Isotopes & Average Atomic Mass :

Isotopes & Average Atomic Mass Because of the existence of isotopes, the mass of a collection of atoms has an average value. 6Li = 7.5% abundant and 7Li = 92.5% Avg. Atomic mass of Li = ______________ 28Si = 92.23%, 29Si = 4.67%, 30Si = 3.10% Avg. Atomic mass of Si = ______________