Science Trial

• Atom


  The building blocks of matter, made up of even smaller particles
• Atom


  • Has a nucleus in the center containing protons and neutrons
  • Electrons orbit the nucleus in shells
• Protons


  Positively charged particles found in the nucleus that determine the identity of an element
• Neutrons


  Neutral particles found in the nucleus that help stabilize it and add mass to the atom
• Electrons


  Negatively charged particles that orbit the nucleus and are involved in chemical reactions and bonding
• Periodic table


  Organizes all the elements based on their properties
• Development of the modern periodic table


  • Mendeleev organized elements based on atomic mass and properties, leaving gaps for undiscovered elements
  • Moseley arranged them by atomic number, the number of protons
• Periods


  Rows in the periodic table representing the number of electron shells an atom has
• Groups/Families


  Columns in the periodic table containing elements with similar properties
• Trends in the periodic table


  • Atomic size increases down a group and decreases across a period
  • Ionization energy, electronegativity, and metallic character change predictably
• Properties of elements


  • Metals are shiny, malleable, and good conductors
  • Nonmetals are dull, brittle, and poor conductors
  • Noble gases are super stable and unreactive
• Reactivity of alkali metals

  Increases down Group 1 as it becomes easier for them to lose an electron
• Compound


  Formed when atoms of different elements chemically bond together
• Chemical formula


  Tells you the types and numbers of atoms present in a compound
• Chemical reaction


  Involves the rearrangement of atoms to form new substances
• Word equation


  Shows the reactants and products of a chemical reaction
• Chemical reactions in living systems

  Vital for processes like respiration and digestion, where energy is released from food molecules
• Factors affecting rate of chemical reactions


  • Temperature
  • Surface area
  • Catalysts
• Male reproductive system


  • Testes produce sperm, which is carried through the reproductive tract and released during ejaculation
• Female reproductive system


  • Ovaries produce eggs, which travel through the fallopian tubes to the uterus, where fertilization can occur
• DNA


  Contains the genetic information that determines our traits
• Mitosis


  Cellular photocopying, where cells duplicate themselves for growth and repair
• Meiosis


  A special type of cell division that produces gametes (sperm and eggs) with half the number of chromosomes
• Gregor Mendel's experiments


  Laid the foundation for understanding how traits are inherited
• Punnett square


  Helps predict the probability of traits in offspring
• DNA structure


  • Double helix with base pairs forming the rungs, allowing accurate copying during cell division
• Atomic size


  The distance from the nucleus of an atom to the outermost energy level that contains electrons. Increases down a group and decreases across a period in the periodic table.
• Oxidation state


  The charge that an atom would have if all of its bonds were completely ionic. A measure of how many electrons an atom has gained or lost in a chemical reaction. Can be positive, negative, or zero.
• Valence shell


  The outer electron shell of an atom
• Stable atoms


  Atoms with full valence electron shells that do not readily react with other atoms
• Achieving stability


  Atoms without full valence shells must react with other atoms by gaining, losing or sharing electrons in chemical bonds
• Factors affecting an atom's chemical reactivity


  • How many electrons it has in its valence shell
  • How far the valence electrons are from the nucleus
• Reactivity


  The easier it is for an atom to gain a full valence shell, the more reactive it will be
• As you move down a group

  Atoms have more electron shells, so the attractive force between the nucleus and the valence electrons decreases
• Metals


  • Have few electrons in their valence shells and will lose these to become stable
  • As the attractive force between the nucleus and these electrons decreases, it is easier to lose them, and therefore the reactivity increases down a group for metals
• Non-metals


  • Have many electrons in their valence shells and will gain electrons to become stable
  • As the attractive force decreases, it is harder to attract electrons into the valence shell, and therefore the reactivity decreases down a group for non-metals
• The elements get more reactive as you move down the group
• The further away from the nucleus the electrons get, the weaker this attractive force. This effect on reactivity depends on which group the atom is in
• Physical properties


  Can be detected by our senses, or otherwise describe the way that a substance is
• Chemical properties


  Describe the way that a substance can change into another substance