what’s the matter ?
DESCRIPTION
What’s the MATTER ?. Anything that has mass and takes up space. What about air …. Slice and dice it to as small a piece you can make it……. atom. Electron cloud. 6e –. +. +. Nucleus. 6. +. Protons. Mass number = 12. 6. Neutrons. –. 6. Electrons. - PowerPoint PPT PresentationTRANSCRIPT
Slice and Slice and dice it to dice it to as small as small a piece a piece you can you can make make it……..it……..
atom
An atomatom has a positively charged center surrounded by a negatively charged area.
+ -
+
–
6
6
6
Protons
Neutrons
Electrons
Massnumber = 12
+ +
6e–
Nucleus
Electroncloud
1. nucleus (positiive region)protons (positive) and neutrons (neutral)
2. electron clouds (negative region)
electrons (negative)
+
+
– –
+
–
2
2
2
Protons
Neutrons
Electrons
Massnumber = 4
+
+
2e–
Electroncloud
Nucleus
3 subatomic particles….. 2 regions
Electrons(-)
It’s electric … no thanks..
neutrons
NEUTRAL
protons
p.p.p.p.p.pppositive
PP ….. Ewe….
ELEMENTSELEMENTS, ATOMS, AND MOLECULES
• Living organisms are composed of about 25 chemical elements
– About 25 different chemical elements• Are essential to life
– About 90 naturally occurring elements• Listed on the periodic table with some
unnatural ones
Atoms and ElementsElements• Horizontal rows are called periodsperiods.
• Vertical columns are called groupsgroups.
•Differences in Elements– Atoms of each element
• Are distinguished by a specific number of protonsprotons
IRONIRON
Atomic number ------- 26
Atomic Mass ------ 56
Protons -------- 26
Neutrons -------- 3030
Electrons -------- 26
– CarbonCarbon, hydrogenhydrogen, oxygenoxygen, and nitrogennitrogen
• Make up the bulk of living matter
•Trace elements Trace elements are common additives to food and water
– Dietary deficiencies in trace elements• Can cause various physiological
conditions
• Which elements are the most common in living things?
a. Carbon, Helium, Chlorine and Sulfurb. Hydrogen, Carbon, Nitrogen and
Calciumc. Carbon, Oxygen, Nitrogen and
Hydrogen
• What’s makes gold gold and lead lead?
a. The number of protonsb. The number of neutronsc. The number of electron
•IsotopesIsotopes– The number of neutrons in an atom may vary
• Variant forms of an element are called isotopes
• Some isotopes are radioactive
Table 2.4
•Electron arrangement determines the chemical properties of an atom
Hydrogen (H)Atomic number = 1
Electron
Carbon (C)Atomic number = 6
Nitrogen (N)Atomic number = 7
Oxygen (O)Atomic number = 8
Outermost electron shell (can hold 8 electrons)
First electron shell (can hold 2 electrons)
– Atoms whose shells are not full • Tend to interact with other atoms
and gain, lose, or share electrons
– These interactions• Form chemical bondschemical bonds
• Why do atoms form bonds to make molecules?
a. To gather more protons for their nucleib. To increase the number of their electronsc. To have a stable number of electrons in
their outermost shell
Elements can combine to form compoundscompounds– Chemical elements
• Combine in fixed ratios to form compounds• Millions of different molecules possible
Sodium Chlorine Sodium Chloride
elementelement
compoundcompound
Pure substance can be found in nature
Pure substance formed when two or more different elements combine.
atom
molecule
MATTERMATTER
•Ionic bonds Ionic bonds are attractions between ions of opposite charge
– When atoms gain or lose electrons• Charged atoms called ions are created
Transfer of electron
NaSodium atom
ClChlorine atom Na+
Sodium ion
Cl–
Chloride ion
Sodium chloride (NaCl)
Na Cl ClNa
+ ––
–
– An electrical attraction between ions with opposite charges
• Results in an ionic bond
Transfer of electron
NaSodium atom
ClChlorine atom Na+
Sodium ion
Cl–
Chloride ion
Sodium chloride (NaCl)
Na Cl ClNa
+ ––
–
•Unequal electron sharing creates polar moleculespolar molecules
– A molecule is nonpolar• When its covalently bonded atoms
share electrons equally
(–) (–)
(+) (+)
O
HH
– In a polar covalent bond• Electrons are shared unequally between
atoms, creating a polar molecule
(–) (–)
(+) (+)
O
HH
Figure 2.9
• Hydrogen bondsHydrogen bonds are weak bonds important in the chemistry of life
– The charged regions on water molecules
• Are attracted to the oppositely charged regions on nearby molecules
(–) (–)
(+) (+)
O
HH
– This attraction forms weak bonds • Called hydrogen bonds
Hydrogen bond(+)
(+)
H
H(+)
(+)
(–)
(–)
(–)(–)
O
• 2. What type of bond is very weak but important to holding together DNA?
a. Hydrogenb. Covalentc. Ionic
• 3. What type of strong bond does salt make from sodium and chlorine?
a. Hydrogenb. Covalentc. Ionic
4. Why do atoms of elements form chemical bonds with other atoms to form molecules?
a. To fill their nucleus with a stable number of protons
b. To fill the outer shell of their atoms with a stable number of electrons
c. To add to the number of neutrons in their nucleus
5. Water is a molecule formed from Oxygen and 2 Hydrogen sharing electrons. What type of bond is this?
a. Covalentb. Hydrogenc. Ionic