A radioactive element is an element which is subject to spontaneous degeneration of its nucleus followed by the emission of alpha, beta and gamma particles. All elements with atomic numbers greater than 83 are radioactive.
The given phrases that describe radioactive elements are-
They have a consistent number of particles
- the particles are alpha, beta and gamma particles.
They have a half-life that determines their rate of decay.
Explanation for other options:
Not all elements occur in nature. Radioactive decay rates may not be constant as the decay happens when a radioactive substance emits a particle. It is not possible to predict exactly when a given atom of a substance will emit a particular particle. When the radioactive element release energy and particles, it decays.
Chordates, or members of phylum Chordata, possess a backbone.
Answer:
False
Explanation:
Gram stain technique is a method use to classify bacteria into large groups base on their different cell wall components. It differentiate gram positive and gram negative by coloring them with red or Violet colors.
Gram stain is use for identification and classification of bacteria.
Gram positive stain violet due to presence of thick layers of peptidoglylcan in their cell walls and gram negative stain red due to thin layers of peptidoglylcan in their cell walls.
