ch 2 building from scratch: atoms and elements

Question 1

atom

Answer 1

the smallest unit of matter capable of retaining the identity of an element during a chemical reaction

Question 2

element

Answer 2

a substance that can’t be broken down into simpler substances by normal chemical reactions

the periodic table

Question 3

how many naturally occuring elements are there

Answer 3

98

only 10 have been observed in trace amounts

Question 4

how many artifically created elements are there

Answer 4

20

Question 5

how many elements are on the periodic table

Answer 5

118 known elements

Question 6

how are the elements organized on the periodic table of elements

Answer 6

by name, symbol, atomic weight, and atomic number

Question 7

the bulk elements are

Answer 7

• oxygen
• carbon
• hydrogen
• nitrogen
• phosphorus
• sulfur

these 6 make up 95% of all living material
remember CHNOPS

Question 8

what are atoms made up of

Answer 8

protons and neutrons
* in the atom’s nucleus

electrons
* cloud of electrons orbiting the nucleus

Question 9

how to find atomic weight/ mass

Answer 9

total number of protons and neutrons in its nucleus

Question 10

what is the atomic number of an atom

Answer 10

its number of protons

Question 11

atoms that are electrically neutral have the same number of

Answer 11

positive charges as negative charges

Question 12

opposite charges attract so

Answer 12

negatively charged electrons are attracted to positively charged protons

the attraction holds electrons in orbits outside the nucleus

Question 13

the more protons there are the in the nucleus the stronger the atom’s positive charge

Answer 13

is and the more electrons is can attract

Question 14

how many electrons can be held in the shells or orbits

Answer 14

• the first shell hold ONLY 2 electrons
• the second and third shells hold 8 electrons EACH
• the fourth shell holds up to 18 electrons (can be found in elements like potassium, calcium, iron)

higher shells are also exist that hold even more electron

Question 15

isotopes

Answer 15

• atoms of an element that have a different number of neurons and a different number of atomic weight than usual
• basically alternate forms of the same chemical element so they always have the same number of protons as that element but a different number of neutron
• the two most common in the body are potassium 40 and carbon 14

Question 16

ions

Answer 16

• atoms that have gained or lost electrons are transformed into ions
• getting an extra electron turns an atom into a negatively charged ion aka anion
• losing an electron creates a positively charged ion aka cation
• the 4 most prevalent are sodium (Na+), potassium (K+), calcium (Ca2+), and chloride (Cl-)
• to keep cations and anion straight think of gaining is negative and losing is positive

Question 17

acid

Answer 17

• a substance that becomes ionized when placed in a solution, producing positively charged hydrogen ions, H+
• considered proton donor
• stronger acids seperate into larger numbers of H+ ions in solution

• atoms always have the same number of electrons as protons
• ions are produced when an atom gains or loses electrons

Question 18

base

Answer 18

• a substance becomes ionized when placed in solution producing negatively charged hydroxide ions OH-
• bases are referred to as being more alkaline than acids
• known as proton acceptors
• stronger bases seperate into larger numbers of OH- ions in solution

Question 19

pH

(potential of hydrogen)

Answer 19

• a mathematical measure on a scale of 0 to 14 of the acidity or alkalinity of a substance
• a solution is considered neutral neither acid nor base if its pH is exactly 7
• pure water has a pH of 7
• the strength of an acid or base is quantified by its absolute difference from that neutral number of 7
• this number is large for a strong base and small for a weak base

• skin is considered acidic; pH of 5
• bloos is considered basic; ph around 7.4