Samenvatting Biology Campbell H2
Atoms and Molecules
Concept 2.1: matter consists of chemical elements in pure form and in combinations
called compounds
Organisms are composed of matter; anything that takes up space and had
mass. Matter is made up of elements.
Elements: substance that cannot be broken down to other substances.
Compound: substance consisting of two or more different elements combined in
a fixed ratio.
Essential elements: 20-25% of all the 92 natural elements, an organism needs
these to have a healthy life and to reproduce. Along organisms the variation of
these essential elements is different.
Trace elements: also known as microminerals, are substances that make up less
than 0.01% of the body mass.
Concept 2.2: an element’s properties depend on the structure of its atoms
Each element consists of a certain type of
atom that is different from the atoms of any
other elements.
Atom: the smallest unit of matter that still
retains the properties of an element
Subatomic particles: neutrons (electrically
neutral), protons, electrons
Atomic nucleus: protons and neutrons are
packed together in the centre of an atom
Electrons: form a “cloud” of negative charge
around the nucleus
Neutron and proton are almost identical in mass (1,7 x 10 -24 gram). Grams are
not very useful for describing the mass of objects that are so minuscule. So, we
use a unit of measurement called Dalton. Neutrons/protons have masses close
to 1 Dalton. The mass of electrons is 1/2000 of a neutron/proton, so we can
ignore when computing the total mass of an atom.
Atoms and Molecules
Concept 2.1: matter consists of chemical elements in pure form and in combinations
called compounds
Organisms are composed of matter; anything that takes up space and had
mass. Matter is made up of elements.
Elements: substance that cannot be broken down to other substances.
Compound: substance consisting of two or more different elements combined in
a fixed ratio.
Essential elements: 20-25% of all the 92 natural elements, an organism needs
these to have a healthy life and to reproduce. Along organisms the variation of
these essential elements is different.
Trace elements: also known as microminerals, are substances that make up less
than 0.01% of the body mass.
Concept 2.2: an element’s properties depend on the structure of its atoms
Each element consists of a certain type of
atom that is different from the atoms of any
other elements.
Atom: the smallest unit of matter that still
retains the properties of an element
Subatomic particles: neutrons (electrically
neutral), protons, electrons
Atomic nucleus: protons and neutrons are
packed together in the centre of an atom
Electrons: form a “cloud” of negative charge
around the nucleus
Neutron and proton are almost identical in mass (1,7 x 10 -24 gram). Grams are
not very useful for describing the mass of objects that are so minuscule. So, we
use a unit of measurement called Dalton. Neutrons/protons have masses close
to 1 Dalton. The mass of electrons is 1/2000 of a neutron/proton, so we can
ignore when computing the total mass of an atom.
