What is the difference between an atom an

What is the difference between an atom, an element, a molecule, and a formula?

What is the difference between an atom, an element, a molecule, and a formula unit? • Atom: the basic unit of a chemical element. • Element: a substance that cannot be broken down into simpler substances and are primary constituents of matter. • Molecule: a group of atoms covalently bonded together • Formula unit: the simplest mathematical expression for a group of atoms ionically bonded together

1. Why is Potassium (K) placed after Argon (Ar) on the periodic table of the elements even though it has a lower average atomic mass than argon? a. Potassium has one more proton b. Argon was discovered first c. Potassium has fewer electrons d. Argon has a lower density

1. Why is Potassium (K) placed after Argon (Ar) on the periodic table of the elements even though it has a lower average atomic mass than argon? a. Potassium has one more proton b. Argon was discovered first c. Potassium has fewer electrons d. Argon has a lower density • A) Because the periodic table is arranged by increasing atomic # (which is the # of protons)

2. When cations and anions join, they form what kind of chemical bond? a. ionic b. hydrogen c. metallic d. covalent

2. When cations and anions join, they form what kind of chemical bond? a. ionic b. hydrogen c. metallic d. covalent a) Ionic bonds are when electrons are exchanged between two atoms, creating ions (cations & anions) that have a + or – charge. This difference in charge results in a strong bond where the ions are attracted together in a crystal lattice structure.

3. Which of the following elements has the same Lewis dot structure as Silicon? a. germanium (Ge) b. aluminum (Al) c. arsenic (As) d. gallium (Ga)

3. Which of the following elements has the same Lewis dot structure as Silicon? a. germanium (Ge) b. aluminum (Al) c. arsenic (As) d. gallium (Ga) a) Ge because all elements in the same group A family have the same # of valence electrons

6. The most abundant isotope of lead contains 82 protons and 124 neutrons packed closely together in the nucleus. Why do the protons stay together in the nucleus rather than fly apart? a. Electrons in neighboring atoms neutralize repulsive forces between protons. b. Neutrons effectively block the protons and keep them far apart to prevent repulsion. c. Electrostatic forces between neutrons and protons hold the nucleus together. d. Nuclear forces overcome repulsive forces between protons in the nucleus.

6. The most abundant isotope of lead contains 82 protons and 124 neutrons packed closely together in the nucleus. Why do the protons stay together in the nucleus rather than fly apart? a. Electrons in neighboring atoms neutralize repulsive forces between protons. b. Neutrons effectively block the protons and keep them far apart to prevent repulsion. c. Electrostatic forces between neutrons and protons hold the nucleus together. d. Nuclear forces overcome repulsive forces between protons in the nucleus. d) the strong nuclear force is what holds protons and neutrons together in the nucleus.

7. Some of the molecules found in the human body are NH 2 COOH (glycine), and C 6 H 12 O 6 (glucose). The bonds they form are a. nuclear. b. ionic. c. metallic. d. covalent.

7. Some of the molecules found in the human body are NH 2 COOH (glycine), and C 6 H 12 O 6 (glucose). The bonds they form are d) covalent. ***Be a. nuclear. able to see the b. ionic. difference between covalent c. metallic. molecules & Ionic d. covalent. compounds

Molecules Na. Cl is ionic; Crystal Lattice; have different shapes Repeating Structure

8. Which of the following is a nonpolar molecule? A) HF B) H 2 O C) CH 4 D) NH 3

8. Which of the following is a nonpolar molecule? A) HF B) H 2 O C) CH 4 draw it! D) NH 3

9. How many electrons are shared in a single covalent bond? A) 1 B) 2 C) 3 D) 8

9. • How many electrons are shared in a single covalent bond? • A) 1 • B) 2 • C) 3 • D) 8 • B) a pair of electrons (2 electrons) is shared in a single covalent bond.

What type of force 10. holds ions together in salts such as Ca. F 2? a. electrostatic b. magnetic c. gravitational d. nuclear

10. What type of force holds ions together in salts such as Ca. F 2? a. electrostatic b. magnetic c. gravitational d. nuclear a) Electrostatic force: the attraction between positive & negative (IONIC!) This is the same force between protons (+) & electrons (-)

11. Which of the following is a monatomic gas at STP (standard temperature and pressure)? a. argon b. fluorine c. hydrogen d. nitrogen

11. Which of the following is a monatomic gas at STP (standard temperature and pressure)? a. argon b. flourine c. hydrogen d. nitrogen a) Argon – all others are diatomic molecules at STP.

12.

12. • Carbon has 4 valence electrons that can make covalent bonds with 4 different hydrogen atoms.

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13. Diatomic molecules are always covalent bonds. Memorize ammonia and methane!!!

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17. Which statement best describes the density of an atom’s nucleus? A The nucleus occupies most of the atom’s volume but contains little of its mass. B The nucleus occupies very little of the atom’s volume and contains little of its mass. C The nucleus occupies most of the atom’s volume and contains most of its mass. D The nucleus occupies very little of the atom’s volume but contains most of its mass.

17. Which statement best describes the density of an atom’s nucleus? D The nucleus occupies very little of the atom’s volume but contains most of its mass. Protons and neutrons are very densely packed in the nucleus.

24. Which of these is an example of an exothermic chemical process? • A evaporation of water • B melting ice • C photosynthesis of glucose • D combustion of gasoline

24. Which of these is an example of an exothermic chemical process? • • • A evaporation of water (heat energy in!) B melting ice (heat energy in!) C photosynthesis of glucose (heat energy in!) D combustion of gasoline (heat energy out!) Exothermic means that heat/energy is released as a product. • Endothermic means heat/energy is added into the reaction

25. If the attractive forces among solid particles are less than the attractive forces between the solid and a liquid, the solid will A probably form a new precipitate as its crystal lattice is broken and re-formed. B be unaffected because attractive forces within the crystal lattice are too strong for the dissolution to occur. C begin the process of melting to form a liquid. D dissolve as particles are pulled away from the crystal lattice by the liquid molecules.

25. If the attractive forces among solid particles are less than the attractive forces between the solid and a liquid, the solid will D dissolve as particles are pulled away from the crystal lattice by the liquid molecules. **Since the attractive forces in the solid are weaker, the solid will dissolve in the liquid.

33. Which of the following atoms has the largest atomic radius? A barium (Ba) B chlorine (Cl) C iodine (I) D magnesium (Mg)

40. The specific heat of copper is about 0. 4 joules/ gram ºC. How much heat is needed to change the temperature of a 30. 0 gram sample of copper from 20. 0 ºC to 60. 0 ºC? A 1000 J B 720 J C 480 J D 240 J

40. • The specific heat of copper is about 0. 4 joules/ gram ºC. How much heat is needed to change the temperature of a 30. 0 gram sample of copper from 20. 0 ºC to 60. 0 ºC? • A 1000 J B 720 J C 480 J D 240 J Q = mc(∆T) Q = 30 g X 0. 4 j/g°C X 40 °C Q = 480 J

A UV ray has a wavelength of 11. 0 nm. What is its frequency?

A UV ray has a wavelength of 11. 0 nm. What is its frequency? v= 2. 73 x 1016 /s 2. 998 x 108 m/s = v 11. 0 x 10 -9 m

Everything you know about SF 4

2 different situations: 1) Uranium-240 undergoes alpha decay. What does it transform into? 2) Uranium-240 undergoes beta decay. What does it transform into?

Uranium-240 undergoes alpha decay. What does it transform into?

Fill in the following: States of Matter – Graphic Organizer Gases Shape Volume Movement Collisions Liquids Solids

States of Matter – Graphic Organizer Gases Liquids Solids Shape of its container Definite shape Volume of its Definite container volume Definite volume Movement Straight until Slide past collision; each other RANDOM Vibrating in fixed positions Collisions The entire near container neighbors and other the container gas particles