An image forming apparatus includes a magnetic toner, an image bearing member, and a development device. The image bearing member is an amorphous silicon photosensitive drum. The magnetic toner includes toner particles. The toner particles each include a toner mother particle containing a binder resin and a magnetic powder and alumina particles attached to a surface of the toner mother particle. The alumina particles each include a core containing alumina and a conductive layer covering the core. The conductive layer contains antimony tin oxide. The alumina particles have a number average primary particle diameter of at least 0.15 ?m and no greater than 0.50 ?m. The alumina particles have a specific resistance of no greater than 250 ?.Math.cm. The alumina particles have an X-ray intensity ratio of at least 0.25 and no greater than 0.35.

A silica particle contains a nitrogen-containing compound, ?/? is 0.30 or greater and 0.80 or less, where ? and ? are the BET specific surface areas of the silica particle before and after baking at 350? C., respectively, and the absolute ratio of the triboelectric series of the silica particle before baking at 350? C. to that of the silica particle after baking at 350? C. is 0.10 1or greater and 0.85 or less.

The present invention provides a toner that can maintain excellent transferability even when a transfer bias is low. The toner includes a toner particle that includes a toner base particle and a plurality of convex portions X existing on a surface of the toner base particle, wherein the convex portion X contains an organic silicon polymer; when a cross-section of the toner is observed with a scanning transmission electron microscope (STEM), and the convex portions X comprise a plurality of convex portions Y each having a convex height H of 40 nm or higher, a number ratio P (H/w) of the a number of the convex portions Y2 in which a ratio (H/w) of the convex height H to the convex width w is 0.33 or larger and 0.80 or smaller is 70% by number or more with respect to a total number of the convex portions Y.

An electrostatic charge image developing toner contains toner particles, fatty acid metal salt particles externally added to the toner particles, and silica particles (S) that are externally added to the toner particles and contain a nitrogen element-containing compound containing a molybdenum element, in which a ratio N.sub.Mo/N.sub.Si of Net intensity N.sub.Mo of the molybdenum element measured by X-ray fluorescence analysis to Net intensity N.sub.Si of a silicon element measured by X-ray fluorescence analysis is 0.035 or more and 0.45 or less.

An electrostatic charge image developing toner contains toner particles that contain a binder resin and resin particles and silica particles (A) that are externally added to the toner particles and contain a nitrogen element-containing compound containing a molybdenum element, in which a ratio N.sub.Mo/N.sub.Si of Net intensity N.sub.Mo of the molybdenum element measured by X-ray fluorescence analysis to Net intensity N.sub.Si of a silicon element measured by X-ray fluorescence analysis is 0.035 or more and 0.45 or less.

Silica particles having silica base particles, a coating structure that coats the silica base particles and is composed of a reaction product of a trifunctional silane compound, and a nitrogen element-containing compound that has adhered to the coating structure and contains a molybdenum element, in which in a molybdenum element map created by SEM-EDX, a ratio of a total area of a region forming a lump having a long diameter of 500 nm or more is 5% or less to a total area of the molybdenum element.

A toner for electrostatic image development includes: toner particles; perovskite compound particles externally added to the toner particles; and silica particles (S) that are externally added to the toner particles and include an elemental nitrogen-containing compound containing elemental molybdenum and in which the ratio N.sub.Mo/N.sub.Si of a Net intensity N.sub.Mo of elemental molybdenum that is measured by X-ray fluorescence analysis to a Net intensity N.sub.Si of elemental silicon that is measured by the X-ray fluorescence analysis is from 0.035 to 0.45 inclusive.

A silica particle is provided in which a pore size distribution curve obtained by nitrogen gas adsorption of the silica particle after baking at 350? C. has at least one peak at a pore diameter of 2 nm or less and at least one peak at a pore diameter of more than 2 nm and 50 nm or less, and D/B is 0.50 or greater and 2.50 or less, where D and B are the volumes of pores having a diameter of 2 nm or less and a diameter of 2 nm or more and 25 nm or less, respectively, determined from the pore size distribution curve obtained by nitrogen gas adsorption of the silica particle after baking at 350? C.

Compositions are provided which may comprise a plurality of organic additive particles, the particles comprising a polymerization product of reactants comprising a dioxane/dioxolane monomer and a vinyl co-monomer, wherein the dioxane/dioxolane monomer is an ester of (meth)acrylic acid with an alcohol comprising a dioxane moiety, an ester of (meth)acrylic acid with an alcohol comprising a dioxolane moiety, or both. Toner and additive manufacturing compositions comprising the organic additive particles are also provided.

A developer including a colored resin particle and an external additive added to a surface of the colored resin particle and having a diameter smaller than or equal to 200 nm is provided. The external additive includes a nitrogen-containing resin particle. In elemental analysis of the nitrogen-containing resin particle, a peak appearing in a range of 0.38-0.42 keV is expressed as an N-peak, and a peak appearing in a range of 0.48-0.52 keV is expressed as an O-peak. Maximum count numbers in the N-peak and the O-peak of the external additive on a surface of the colored resin particle are respectively expressed as N1 and O1. Maximum count numbers in the N-peak and the O-peak of the surface of the colored resin particle where no external additive is observed are respectively expressed as N2 and O2. The count numbers N1, O1, N2 and O2 satisfy 1.7(N2/O2)<(N1/O1).