ELEMENTS
PRESENTATION 1: WHAT ARE ELEMENTS?
Text
what elements are in an elephant?
the PERIODIC TABLE
WHAT DO YOU KNOW ABOUT THE
TABLE OF ELEMENTS?
ELEMENTS...
are PURE chemical substances...
consisting of one type of ATOM...
distinguished by an ATOMIC NUMBER....
which is the number of PROTONS in its nucleus
what are the atomic
numbers of these
elements?
this is CARBON
all elements have a unique symbol
the mass number tells you how many
protons and neutrons are in the nucleus of
the element
the atomic number tells you how many
protons are in that particular element’s
atoms
ELEMENTS ARE FURTHER DISTINGUISHED BY THEIR
PHYSICAL PROPERTIES
• Density:
• Melting point / boiling point
• For metals:
– electrical conductivity
– malleability — whether it squashes or cleaves when struck
with a hammer
– ductility — whether it can be drawn into a wire
• Physical state at room temperature (liquid, solid, gas)
• Appearance (e.g. colour, surface texture, lustre)
lets have a
look at
gold...
solid
metal
density = 19.30 g /
3
cm
boiling point = 2856 °C °C
malleable, ductile, soft, shiny
melting point = 1064.18 °C
these physical properties of gold are why
it’s worth:
$58,940 / kilogram!!!!!!
ISOTOPES
Atoms of the same element can have different numbers of neutrons; the
different possible versions of each element are called isotopes. For
example, the most common isotope of hydrogen has no neutrons at all;
there's also a hydrogen isotope called deuterium, with one neutron, and
another, tritium, with two neutrons. An example of an isotope is C-13
Hydrogen
Deuterium
Tritium
ordinary hydrogen is written 1H1, deuterium is 2H1, and tritium is 3H1
1. Isotopes of an element have
a. the same number of neutrons
b. the same number of protons
c. a different number of protons
ISOTOPES QUIZ
2. The isotope carbon-14 has
a. 6 neutrons
b. 7 neutrons
c. 8 neutrons
3. Cu-63 has a mass of 62.9396 amu and relative abundance of 69.50%.
Cu-65 has a mass of 64.9278 and relative abundance of 30.50%.
What is the weighted average atomic mass?
a. 62.5460 amu
b. 63.5460 amu
c. 64.3213 amu
4. An isotope of manganese has 25 protons and 30 neutrons.
What is the mass number of this isotope?
a. 25
b. 30
c. 55
ISOTOPES QUIZ part 2
The mass number is the sum of...
A: the electrons and protons
B: protons and neutrons
C: neutrons and electrons
Isotopes differ in __________, not atomic number.
A: mass
B: volume
C: density
How many protons are in mercury-204?
A: 204
B: 80
C: 124
How many neutrons are in uranium-238?
A: 146
B: 92
C: 238
How many neutrons are in potassium-40?
A: 19
B: 40
C: 21
notes:
atoms consist of three basic subparticles:
- proton (+ charge)
- neutron (neutral charge)
- electron (- charge)
- The Bohr model states that atoms have a dense nucleus of protons
and neutrons (nucleons) surrounded by electrons traveling in orbits at
fixed distances
- Nuclides are atoms that contain a particular number of protons and
neutrons.
- Isotopes are nuclides that have the same atomic number (and are the
same element) but have different numbers of neutrons
- the atomic number of an atom is the number of protons in
the nucleus
- the mass number of an atom is the total number of
nucleons in the nucleus